Safe Mode. You could also try going via "last known good configuration" in same menu. How to start in Safe Mode:
My Temptation would be to go SFC route first. Please let us know results.
How old machine & HD? What AV & Anti-malware have you (exact versions & last updates, please)& anything else weird happening.
I assume it is an XP problem. My HP was working fine all day and then I closed applications, cam back, and I cannot open anything. IE, MSN, Word, you name it and I double click and it goes to hour glass and glass leaves and.....nothing. Only programs on start up are available - clock, weather, wireless connection. I go to start and any program or file will not respond with no messages. I can bring up TASK manager as I thought something was there that would be a problem...nothing. The one thing I can open is My Docs folder but cannot open anything in it?
I had this thing cleaned out and added ram 2 years ago and do not use too much (new mac took its place due to issues like this) but I still use it for email....HELP Please.