If you mean that your computer is freezing as soon as you start up then it probably means that some software which is loading in the background is conflicting with the operating system or there is a currupt OS file. You need to start in safe mode, which will load windows in a minimal configuration thus not loading anything in the background. If the system works in safe mode you will need to discover what is loading to cause the freeze by a process of elimination. If you just installed something before this freezing started to happen start by uninstalling that program and restart. If you are using windows Me or XP you can do a system restore to a point in time which you know the system was stable. If you are using an earlier OS then try working through the systems troubleshooting guide.
Flashman, June 2004