I gather that your Virtual memory is a "SWAP" file on the hard drive which is used to store required information when the RAM memory is getting full and it should be about one and a half times the size of your RAM.
You don't say what system you are using but in XP you can Right Click the MY Computer icon on the desk top, click Properties, click Advanced, in the Performance box click Settings, click Advanced and in Virtual Memory section click CHANGE.
Make it one and a half or twice as large as your RAM memory.
Hope this helps.