Start > Run > type in MSCONFIG
Go to the startup tab, and disable anything besides Firewall, Antivirus, or anything else you definately need on startup.
Honestly, it's not going to get too much better. Windows itself uses a massive amount of memory just to keep your screen up. You can also use the tab next to startup (forget what it is) and turn off "themes" and that will free up a lot of memory - but windows will look like 5.1 and not be very attractive anymore.
For my startup, all I have running are Zonealarm, and Norton. Play with it a bit and see how you like it. Be sure to WRITE DOWN what's checked on the list BEFORE you start messing with it - that way if you lose functionality in a program you can restore it to what it is now, and start testing one item at a time.