Can't start in Safe Mode

[Syxx_Killer]

I'm running Windows XP Pro with SP2.

It basically started when I wanted to scan for spyware. I start Lavasoft Ad-Aware and can't update. It stops responding. I then update and scan with SpyBot. It found nothing alarming. I then went to Lavasoft's website and looked at the FAQ. Nothing, except downloading and manually installing the update. Did that and all Ad-Aware found was some cookies. I then scanned with Norton Antivirus 2004. It found two instances of some adware called Adware.Istbar. It couldn't delete them. I then clicked one of the items and it took me to the Symantec site. I downloaded a utility they said to use and it didn't find any instances on the computer. Now I'm really confused. I quickly run NAV2004 again, and it again found two instances of Adware.Istbar. I then try to start in Safe Mode. I choose Safe Mode and it shows a list of files and then I get the blue screen of death. I then restart in normal mode. What's going on? I recently had the computer crash about two months ago. I really don't want to have it crash again. Help is appreciated!