Computer kicks me out and goes to a blue screen telling me to restart b/c of bad file?

What can i do to fix that problem when i go to websites or just on the computer it randomly kicks me out and goes to blue screen and tells me i should restart because of bad file...sometimes its "mssync20.sys" and sometimes it says something else....what can i do to fix this problem and I dont have a xp restart disc or any xp software