You may need to boot up into windows safe mode before you can run your antivirus... If it won't boot at all, go to another computer, then download and install Avast anti-virus onto a flash drive... Then put your emergency disk into the CD-ROM (or the floppy, depending on what you created it on), and then run Avast from your stick... Make sure you set it not to scan the CD-ROM and/or floppy drive...
After all that, you may need to restore a backup of your registry (although very few people actually back theirs up for some reason)... Advanced warning though, trying to restore a corrupted registry is a guaranteed will contribute greatly to massive hair loss...
The easier way, if you use any kind of backup/imaging software such as Acronis, would be to do a full restore...
About the only other option that I can think of off the top of my head is going to be a complete reformat of your hard drive and reinstallation of all your software, but that also means that anything you have on your computer like pictures, music and documents is a goner...
Good luck...
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The Lord helps those who help themselves...For everyone else, there's Democrats...
looking for help always! everytime i restart my comp i get registry recovery from alternate file? trying to learn. 
