The "Read Error - Boot Sector" from AVG could be a 'bug' in AVG itself rather than a boot sector problem on your PC.
AVG had this exact bug reported in '95 & '96 after an update, and the same bug may have raised it's head again with another update.
The workaround from them (prior to the fix) reads:
"Boot Sector of Disk C: Reading error" issue was already replicated in our teslab and our developers are working on it.
Do the following to fix it for now:
1) run AVG Test Center (double click the AVG desktop icon)
2) choose "System Areas Test Settings" option from "Tests" menu
3) press "Remove Boot" button
4) confirm OK"
The above is simply so you can perhaps prove that the boot sector error is nothing more than an AVG programming bug, so you don't go "barking up the wrong tree" in an effort to find a solution to your Windows startup problem.
In any event, if the boot sector really was damaged, infected or whatever, Windows wouldn't even start in safe mode, further proof that the boot sector error is a spurious one falsely generated by AVG.
A virus sufficiently potent to stop Windows running doesn't know the difference between normal mode and safe mode. In other words, if a virus stops Windows running, it stops it in both modes.
When only safe mode runs, it usually indicates a Windows update which doesn't 'like' your system, or a driver update which also doesn't like your system, or even an application you've added which installs drivers which aren't compatible with Vista. Drivers are usually the main suspects where only safe mode is usable, because in safe mode none of the third-party drivers are loaded into memory, and amongst those will be the bad one that's causing the problem when Windows (in normal mode) tries to load it.
My daughter's new Vista laptop last week would not start normally but would run in safe mode. Not being in the mood for what could have been a long "process of elimination", I went for the easy option and used 'System Restore', choosing a date just before an automatic Windows update had been installed 3 days earlier. The PC rebooted itself and voila! -- normal service was resumed. You may have the same good fortune......................
Start->All Programs->Accessories->System Tools->System Restore.
The date you choose to 'roll back' to is important. Obviously choose one that you know pre-dates the appearance of your problem.
Edited by pip22, 14 November 2007 - 01:42 PM.