Can't get computer to go into stand by.  A Dell, about a year old with XP home sp2. It has never had standby issues till now.  I have the bios all setup for acpi and windows all setup with that too.  the bios is set for s3 for standby mode (the only other choice is s1 or nothing at all).  

Just added a linksys wireless card WMP54G.  The hardware/driver properties had the thing in CAM mode, so I set it to Max Power settings.  I figured it was the card device driver not letting the system sleep.  That did not work.  I checked the device props and it does support power modes s0,s1,s3,s4,s5.
For modes s3 - s5 the driver uses d3.

I tried disabeling the card in device manager and that did not do the trick.  I also updated the system bios for fun. I looked for a new driver but all the linksys drivers are dated 2003.  Short of removing it....

Only thought that comes to mind is wake on lan..... With wireless there is a "heartbeat".  It may keep it from standing by.  Check for anything to do with "wake on lan", "wake on network activity" etc....

Figured it out.

I wasn't the wireless card.

It was a device driver installed by Intuits Quicken.

mrtrate.sys.   *tinfoil*  why the fuck does accounting software need a device driver?  *tinfoil*

I removed the driver from the register, deleted the files and all is well.