Virtual memory is when windows uses a certain amount of your hard drive space for memory. Usually Windows will manage this by itself and you don't have to worry about it. But, if you're running Windows ME i would recommend setting the virtual memory yourself because of free space errors, which seem to be common with Windows ME. If you let Windows manage VM, the size of it will grow and shrink according to what application you are using at the time and what Windows decides to allocate. The problem i was having(with ME) was that this constant growing and shrinking was producing many a free space error, especially when playing games and would mess up my shutdown at times. So what i did after thinking about this for a while and why it was happening was go into the virtual memory setting and set it myself. I didn't do any fancy calculations to determine the size, i have 384 megs of PC133 ram and i decide to set my VM to a max of 300 megs and a minimum of 300 megs. Why make the max and min the same you ask? This way the size always stays the same it will not constantly grow and shrink and thus will not create free space errors. Ever since i did this i have not gotten a free space error, i kid you not, and never had a problem shutting ME down again. The other plus to setting the size yourself is that Windows will put that chunk of space at the beginning of your drive and it will always stay there, thus cutting down on fragmenting greatly. If Windows manages the VM it put's it all over the drive increasing your chances for fragmenting. That's about it.