To re-clarify for non-techies, to get into plain-vanilla 'Safe Mode' when Windows is starting, hit CTRL-F8.

I don't know if this is the original problem, but for what it's worth: C drives rapidly get filled up with crap and if you have only a meg or two left it makes it difficult for anything to proceed. Trying to defrag a drive with little space or elbow room to work is like trying to paint the floor of a room which is 95% covered with furniture. You have to keep stopping and moving furniture and then you can only paint a little at a time. I don't know if this has anything to do with your situation, but it has bogged me down a time or two. One of the files Windows used to create is a hidden "swap" file which can be enormous, the equivalent of having a grand piano in that room.

Apologies to real gurus if this is technically unsound info...