I am finding that ideally the aperture should be set around 128 mb. The apertures can be set from BIOS, but your computer may be too old. There is a method to change from within Windows, but it's complicated and can no doubt break things. And it only seems to work with VIA hardware. What's worse, I'm finding the files and patch all but gone.
Perhaps if you search around, you can find out more about WPCREDIT, and the other files necessary - I was able to find a download for them, but have no idea whether they'd work for you, or if there is a different set of instructions for each chipset.This
may give you some ideas.Here's