There's an old saying that if something sounds too good to be true, then maybe it is.  Now, that's not always true.  Take Microsoft's free antivirus/anti-malware protection Microsoft Security Essentials works well and is free to Windows users.  However, that old adage might hold a bit more true in the case of AVG, a top free antivirus software maker.

AVG, which claims to have 110 million customers in 170 countries, on Wednesday rolled out a badly botched update.

The update rendered both Windows 7 and Windows Vista inoperable.  When booting users are greeted by the infamous "Blue Screen of Death" (BSoD), and the system reboots in an endless cycle of bad computer karma.  The mess is apparently caused by an AVG .sys file that is loaded at boot time -- \Windows\System 32\DRIVERS\AVGIDSEH.SYS.

Booting into Safe Mode does not work, as this driver is still loaded, under AVG's default setup.

Users are infuriated.  One writes on the companies support forums:

You are not alone!!! This happened to my computer also. I was able to restore it to a restore point, but I will not update. I always supported AVG and recommended it highly. Not any more. It's the same as installing a virus instead of removing one!!! Removing it now - there are other free anti-virus software out there - they just won my support!!!

Another adds:

Just adding my voice to the chorus of those whose computers are unable to reboot after this update. Thank god for Windows 7 auto-backups. I've already sent an email out to my parents who use AVG not to update. I'm about 20 minutes from just sC**pping AVG for good over this. I know, it's the free version so they aren't really losing anything, but this is the sort of computer-destroying problem that you can't even give away.

Those affected shouldn't despair, though.  There are a couple of ways to fix this problem.

One way to save your Windows install if you received the update is to have a Windows install DVD and boot in recovery mode, rolling the system back to a restore point.  If you don't have a Windows install disk or weren't saving restore points you're out of luck.

Another, perhaps better method is to use an emergency USB boot-fix that AVG rolled out.  Full details can be found here, but basically you need to copy the file to your USB stick and then enter the BIOS and tell your computer to boot to the stick.

AVG suggests then repairing your installation of AVG software with the fixed version that they've uploaded, as detailed here.  Or, better yet, you might want to uninstall AVG and go for a more reliable solution, given the company's shoddy track record.

After all, this isn't the first major screwup for the company.  In late 2008, the vendor rolled out an update that accidentally removed a critical Windows component which it mistook for a piece of malware.  Honestly, these kind of errors simply aren't acceptable for a security firm with 110 million users, many of which are paying customers.  

Then again, the allure of free may keep some coming back to AVG.