Fatal bug question

I had installed ESET Smart Security (all updated) and it was working fine. Some time ago I checked an exe for viruses and it came out clean. But, on running it, I saw the waiting hourglass, then nothing. Then many executables (with names like "b.exe") appeared all over (C:, D:, in archives even). I've tried opening NOD32 but it wouldn't start (ekrn.exe was started but no UI appeared). (BTW, when in a browser, every site was working except for Eset.com, Kaspersky.com etc.). I've uninstalled NOD32, then tried reinstalling it. It wouldn't reinstall- at around 60% it said something like "can't access destination directory". I've noticed that that happens only (but always) when there is a virus. Then the computer became very slow and I was forced to reinstall Windows.
Some questions:
1) I scanned the file by right-click> Scan for viruses. Is there other (better) way, since the first one was not efficient?
2) Why did NOD32 not appear when double-clicked? Because of the virus?
3) Is it possible for a virus to block certain internet sites?
4) Is it possible for a virus to block an anti-virus' installation? What could I do?
5) Any other ideas? (For Nr. 2) especially, because not being able to de-virus exactly when there IS a virus is very bad.)

Thanks.

 

b.exe is usually a variant of FakeAlert and ESET is usually among 1-3 AVs to detect it among first. Of course, if you are hit shortly after a new variant is released and before detection is added, it's necessary to remove it which may not always be an easy task. Try starting Windows in safe mode, renaming the file, booting in normal mode, updating EAV and carrying on a full system scan with EAV updated.

 

Thanks, but I still don't know what to do if:
a) I don't know which one is the virus executable among the dozens of other executables it has created, so I don't know which one to rename
OR
b) It happened that it couldn't even get into Safe Mode (the virus again, I guess).
Could you tell me what to do then? Or point me to a de-virusing FAQ or resources on the net?