check this thread for how to boot in safe mode on a dell
http://answers.yahoo.com/question/in...2151724AA2RKaO
anyhoo if its a virtual memory issue that implies ram, open up the ram slot on the bottom and swap the sticks around (thats assuming theres two) try it with one stick then the other one also as one could be causing the trouble.
to get them out theres a cover possibly labeled ram with one or two screws on it and and some little clips inside that if you open the ram should just spring out. only hold it by the sides not on the metal, wear medical gloves or earth yourself if possible. tp put em back in insert them at around 30 degrees (angle not temp :P) and push gently. its obvious when you get it right.
If it is a software issue and your happy to wipe the system and start again lose all your files just put in your xp cd do a fresh windows install format the hard drive etc. Takes about an hour tops.