If it's telling you your C drive is full then it's nothing to dio with virtual memory. That's something else.
First thing I would try is Disk Cleanup.
Here is a article on using it. That should hopefully free up enough space.
Alternatively, do you have a zip utility (e.g. WinZip, WinRar, 7Zip etc.) on your PC? If so you could try zipping up some of your documents, pictures etc. to free up some room (if there's enough room to create the zips that is).
How about putting things onto a floppy disk?
If all these fail, you're just going to have to bite the bullet and start deleting things you want but could do without - e.g. MP3s, old documents etc.