Ok here is the deal.

My PC: a 900MHz AMD processor, running Windows 98SE, it has 256MB RAM in a single 168pin SIMM SDRAM.  It has a SIS 730 & 950 chipset running the peripherals.  I am using the FATS 32 bit fiel system.  The machine is 2-3 years old and was built by one of the local computer shops.  Last year the power supply went tits-up and I replaced it, this weekend the power supply when tits up again (this time I replaced it with a unit with a 5 year warrenty rather than the cheap Comp USA brand I used the first time).

What's going on:  Occasionally I get an error "Unreliable XMS memory @ 00110038 Himem.sys can't be loaded'.  This stops the boot process and I have to reboot.

More often I get errors that it can't find a particular .DLL (for example one time it indicated the MPR.DLL)  but it's never consistant on which Linked Library it can't find.  Now when I DO get it up and running it's not stabil.  Lately it's been having problems running one of my kids favorite games.

Most (but not all) of the stability problems occured when I installed McAffe's Virus software, then when I tried to remove the software the problems got better for a while, then worsened.

What my plans are: I want to upgrade to Windows XP (I have the software package).  But when I tried to run it last night (2 different times - once to check to see if my unit was compatible - and it crashed, and once to try to install it - machine locked up) I had problems.

What I'm considering doing:
1) Replace potentially falty DIMM with a new 512MB 168 pin DIMM SDRAM.  That should fix any issues with the memory and it will double my RAM (fix & upgrade at the same time).

2)Get a new hard drive and set it as the primary, keep my current hard drive.

3) Install Windows XP on the new hard drive using the FATs 32 file system, then copy my needed files from the old hard drive.  Once the files are copied, wipe the old drive, upgrade to the NTFS file system for both drives and use the old drive as a 'shared storage' for my wireless network (currently this PC and my wife's laptop share the internet connection).

Questions:
1) Can I make the current hard drive the 'secondary' when in install a new blank hard drive?  I'm pretty sure I'll have to go into the CMOS setup.

2) Is this feasible?  Is there a quicker/easeir way to fix this problem?  (In any event I am going to upgrade the OS to XP)

3) I may not be able to boot the computer again (it took a dozen boots last night to get it up and running - till I crashed it).  Will I be able to install the new OS (it's the upgrade version) onto the new harddrive w/o booting up?  If so how?

Thanks!

Thanks for the tips.  I'll try (no guarantees on the computer running long enough to run the tests).

i agree test  or replace the memory and then we will talk   memtest86  is another one to try

Quoted: i agree test  or replace the memory and then we will talk   memtest86  is another one to try

Ok I downloaded the memory test onto a bootable CD at work.  Tonight I'll go home and test the memory and get back to you all.

Thanks guys!  I appreciate the help.

download the ultimate boot disk, it has a whole bunch of great programs including memtest

When you get around to your XP load, just format the new drive as NTFS.  You will still be able to mount a FAT32 drive, and you won't have the trouble of converting the drive.

SmilingBandit thanks for the tip I'll tgry that. Now the version of XP that I have is the home "update" version supposedly it checks the system to verify I have an earlier version of Windows.  Will it make a difference if I want to install it on a new hard disk?  Or should I install 98 on the new drive prior to installing XP?

Anyway I ran some tests last night as Art & Cuze suggested.  I ran Scandisk on the disk to check the system files (it kept restarting when I tried to run it on the whole diskeven though all programs were shut dow).  Anyway it showed no problems (yes I also had it check the media).

The memory test was a different issue.  The two RAND tests showed errors, the more the tests were run (total of 7 passes) the more errors were found.  So I'm guessing it's time to replace the SDRAM DIMM?

Are all 168 pin SDRAM DIMMs interchangeable?  I want to go from a 256MB unit to a 512 mb card.  Another related question, my motherboards manual indicates I'll need either 2 'SS' type 512mb cards or 1 'DS' type 512 MB card.  I don't see any 'DS' or 'SS' listings when I look for memory.  Anyone know whats up with this?

Ok I kept the PC on since the last test, and when I got back to it I noticed the 'blue screen of death'.

So I rebooted and used the memory test.  Now I'm getting all kinds of failures during the first Random test and I'm getting failures on the pattern test after it.

I really doubt if my new memory is failing already, could it be a heat issue?  One of the sims had to be installed just about touching the heat sink for the CPU.

if you have multiple sticks of ram.  take one stick out at a time untill you find the one that is bad

or if when you are looking at the test if it fails at the begining of the test from 0-128 mb.   its usually the first memory chip is slot 0, or slot 1 depending on how its labeled

DS = Double sided       has memory chips on both sides

SS = Single sided         has memory only on one side

Quoted: Ok I kept the PC on since the last test, and when I got back to it I noticed the 'blue screen of death'. So I rebooted and used the memory test.  Now I'm getting all kinds of failures during the first Random test and I'm getting failures on the pattern test after it. I really doubt if my new memory is failing already, could it be a heat issue?  One of the sims had to be installed just about touching the heat sink for the CPU.

woops didn't see this,

if its failing new memory you either have incompatible ram, or your memory slots have gone bad.  

Thanks Cruze for chiming in!

Ok original testing indicated bad RAM.  At the time I had a single 256MB DS 133Mhz stick, in slot S0.

(interesting to note my PC thinks I have 3 slots - yet only 2 exist on the board S0 & S1 - the support chips must be able to handle a 3rd bank (S2) but it was never implemented on the motherboard).

I went out and purchased 2 more 256MB DS 133MHz sicks (identical to the original).

When cold (i.e. starting from room temperture) they test out fine and work great.  But once things have been going for a while they start returning errors.  To compare to the original stick - the original would give 2 errors when cold - but many many more once 'warmed up').

So I checked the tempertures when the new memory was failing.
CPU was 160deg C, the System temp was 64deg C.  Note the memory temp should be highter than the system temp as the stick that is in slot S0 is just a hairs bredth away from the CPU's heat sink.

I should note my PC has an optional temperture shutdown that I can set.  The first cut-off is 60deg C, the second is 65 deg C, the highest I can set it is 70 deg C.  So with a couple of hours of run time I'm already past the first one and really close to the second.

Tonight I'm going to start up the machine with the cover removed and see if I can take a temperture near the memory or see if the CPU fan has failed (and it's just getting too hot in that area causing failures).  Does this make any sense?

I would check the fan.  60C is kinda hot(90 is the max it can handle before frying) my bench machines at work are all AMD's and with retail box fans.  they don't get above 40C.  

Cruze,
I checked the fan at 7:45 and sure enough it was dead.  I was at CompUSA by 8 and by 8:30 the new fan was installed.

It's running fine at just over 5700 RPMs

Best of all I ran 1 pass of the Memory check and all the errors I got earlier were gone as now the area is cooler.  So far the system has been running on Windows for 45 minutes or so and has been stabil even when running large memory tasks (scanning in large color images).

All Right!  Looks like she's functioning fine again, now onto upgrading the hard drive and to Windows XP!

Many thanks to all who helped - especially Cruze5!