you can increase the Paging File
right click My Computer
-> settings (performance)
-> change (Vitual Memory)
paging file is a file on the hard drive used as RAM.
the advantage is the ability to increase virtual memory
the disadvantage is the speed of the hard drive. it is much slower than normal RAM.
for that reason, I disable paging file on my system completely. but I have 1GB RAM, and I wouldn't recommend disabling it if you have any less than about 768MB RAM, unless you really do not run enough programs to take much RAM