Virtual memory on Win XP

Usually Virtual Memory should be set to 1.5 timesthe amount of ram you have (2 times if you have a big amount

By default, Windows XP sets the initial size of the page file to 1.5 times the amount of RAM in your system, and it sets the maximum size of the page file to three times the amount of RAM. For example, on a system with 256 MB of RAM, the page file's initial size will be 384 MB and its maximum size will be 768 MB. The default values work well on most systems, but you may want to customize these sizes to suit your own configuration. Here are some notes about custom page file sizes:

The less RAM you have, the more likely it is that Windows XP will use the page file, so the Windows XP default page file sizes make sense. If your computer has less than 512 MB of RAM, you should leave the page file sizes as is.
The more RAM you have, the less likely it is that Windows XP will use the page file. Therefore, the default initial page file size is too large and the disk space reserved by Windows XP is wasted. On systems with 512 MB of RAM or more, you should set the initial page file size to half the RAM size, while leaving the maximum size at three times RAM, just in case.
If disk space is at a premium and you can't move the page file to a drive with more free space, set the initial page file size to 2 MB (the minimum size supported by Windows XP). This should eventually result in the smallest possible page file, but you'll see a bit of a performance drop because Windows XP will often have to dynamically increase the size the page file as you work with your programs.
You might think that setting the initial size and the maximum size to the same (relatively large—say, two or three times RAM) value would improve performance since it would mean that Windows XP would never resize the page file. In practice, however, it has been shown that this trick does not improve performance, and in some cases can actually decrease performance.
If you have a large amount of RAM (at least 1 GB), you might think that Windows XP would never need virtual memory, so that it would be okay to turn off the page file. This won't work, however, because Windows XP needs the page file anyway and some programs may crash if no virtual memory is present.