For BIOS:
Use the optimized (fast) settings, and run your computer heavily (play really powerful games, 3dmark it for a few hours, Sandra it for a few more hours) and see if it holds up. If it crashes a bunch, set it to failsafe. Then use this guy's settings for optimal graphics performance:
http://www.omegacorner.com/bios.htm
Check his 'archives' for more tips for performance gains (and how to hook up some serious bass if you want

).
Next, go to Start>Settings>Control Panel>System. Click the performance tab. Click virtual memory, and specify your own. Choose the fastest drive on your system (if you have more than one). You have 1024mb RAM, so you don't need much. You'll needto put the same number in the maximum and the minimum spaces. I'd put 512 mb in there, just to be safe. If you do alot of mulitasking with stuff like video editing, photoshopinbg, audio editing, and/or gaming, go for 768 or 1024. DO NOT PUT DIFFERENT NUMBERS IN EACH SPACE. Otherwise, you will have a performance hit and will probably have to defrag more than usual. Restart, and get back to the system window.
Click the 'Device Manager' tab. First of all, look for any icons with yellow or red icons at the lower-left-hand corner. Report any to us if you find them. Now click next to 'Disk Drives'. You should see something like:
GENERIC DISK TYPE IDE47
listed there (Or you will see the actual mfg name and model ## for your HDD, depending on how advanced your IDE controller). Click on one (if there are multiple), and then click properties. Click settings. Make sure DMA is checked. Click OK, and repeat for all of your hard drives (not the floppy drive though). Click OK on the System Windows when done, and restart.
Now head to
www.outertech.com, and download Cacheman (whatever the latest ver. is). First off, go to Options, after installing it, and tell it to NOT load on system startup. Then go to Settings. Click Profile. Now click Show Wizards at the top, and click 'All'. Go thorough it and make your choices carefully. Do have it automatically set your cache, set your path cache to the large amount, set the large icon cache (helps stop the icons from suddenly morphing into other random icons), do unload DLLs, and DEFINATELY turn on Conservative swap file (you have MORE than enough RAM to do that). Set the VFAT contiguous allocation size to large, choose which read-ahead best fits you (I would just leave it to default, but that's me), set your IO buffers to max, and optimize all the 3 final settings. Click File>Save Settings, and reboot the machine.
That should give your biggest performance increase. Now head to a few sites to get some smaller, but styill awesome, tweaks:
www.omegacorner.com - Contains Quality-optimized versions of ATI, Nvidia, and 3DFX drivers for downlaod. They are, however, NOT official, so be warned. He also has some nice tweaks in his 'Archive' section.
www.pureperformance.com - Tweaks galore for windows.
http://www.beemerworld.com/tips/ - Written by resident TechIMOer Beemer. Very comprehensive, and has great links to more tweaking sites.
Be warned, many of the tweaks listed are 'Registry Tweaks'. If it involves running a program called 'REGEDIT', you'll need to backup your registry first. Simply load that program, and tell it to export your registry to a file (save it somewhere you will remember. In C:\WINDOWS is a good place). If a registry tweak messes up your system, or if you mess up, then you have a backup.
Oh yeah:

WELCOME TO TECHIMO!!!
-edit- BTW: The cacheman thing you did modifiedyour cache, so unless you want to try some other ways, you already optimized all of the maches mentioned in the program.