Avast Updates---> Computer cannot start up!

After being away for the weekend, I arrived back today (Sunday, 2/5/06) and turned my computer on. Avast notified me that the virus definition file had updated, and then the green “New Version Available” popup came up, and so I clicked it and the version update process completed successfully. Afterwards, it prompted me to restart, and I did. When this happened I had only been running a few IE windows, which I closed before shutdown.

The problem arose during the reboot sequence. The computer will display the initial BIOS flash screen, then the windows logo and progress bar screen, just like normal. At this point in the startup process, the screen will briefly go black and then the login screen, where you choose a user account, will appear. But now, the screen goes black, a pointer appears, and that’s it. No login screen, no finished startup, nothing. Starting in safe mode does nothing; it goes to the exact same black screen, as does using Last Good Configuration from the advanced boot menu.

No matter how many times I restart my computer, all I get is this same situation. According to the Microsoft support website, my only remaining options are using the recovery center (which is pretty much beyond me) or reinstalling the OS (I don’t have the support CD that came with this computer). Has anyone else had this problem? Is there a way I can use the recovery center to rollback the change? Is the avast update the problem, or is it something else?

Please help!

The system in question:
Fujitsu N-Series laptop
2.6ghz P4
512 mb ram
Radeon 9000 mobility
Onboard audio
XP Home SP2
avast!4 Home

If there was a bug in the new avast! version, it shouldn’t affect the safe mode (where avast! is not loaded)…