Why does my laptop always show "virtual memory too low"? How do I fix it?

When I try to reboot, it usually shows a message asking me to "end program" (avp.exe) and sometimes a program called "n" (but I don't have any programs/files named after "n" on my laptop. I'm using Windows XP, Kaspersky anti-virus and have over 6GB free hard disk space. I also did a full scan for any viruses but didn't find anything.