Win32:Small-BTX [Trj] (How did I get it and will it cause permanete damage)

Hey all,

I have been having several pc problems lately. I need to know some info and get to the bottom of what’s going on. I had a virus simular to this on my pc the otherday, avast found it and I deleted it. Then the real trouble began. My pc was FINE this morning, then I went to my college classes and came home. I was going to check my emails but my pc was acting strange. Avast wouldn’t start and it kept saying it was corrupted, then my windows 7 theme standard was changed to windows classic and the icons on my taskbar were gone. I couldn’t even put icons on it at all after that. I was frustrated but decided it was best to just to wipe the drive, reformat, and install new. First thing I did was install avast free and malwarebytes, they were a few weeks old installers but I figured it would work just fine. I then did a full system scan with each and found nothing. So I connected to the net and updated windows, installed firefox, and flash player. I only went to sites with GOOD avast webrep ratings and my normal sites. I updated avast and malwarebytes and ran a full system scan again. Malwarebytes didn’t find anything, but avast found this “Win32:Small-BTX [Trj]” in my temp files. I have NO IDEA how it got on my pc that quick or how it got around malwarebytes and avast’s realtimes scanners.
I guess what I want to know is the following:
1: How did it get on my pc?
2:Will this cause permanent damage to my pc?
3:Does this have the power to gain control of my pc or accounts for websites?
4:Is it gone for good or will it come back?
5:What can I do now to keep from having any problems?

Thank you for your time in reading this. Hope someone can help.

no security programs have 100% detection…
you say it was in temp folder…was it IE temp…maybe it came from a website!
it can also be a false positive? upload files to virustotal.com and test

W32/small
http://www.microsoft.com/security/portal/Threat/Encyclopedia/Entry.aspx?Name=TrojanDownloader%3AWin32%2FSmall

if you need help this is how to. http://forum.avast.com/index.php?topic=53253.0

Thanks Pondus For Replying,

I already deleted it from the computer, so I can’t send it to that site. I doubt I would have gotten it from a website by using IE, I installed FireFox from a disc I made about 5 or 6 days ago and never even used IE on this computer after this reinstall. I have no idea how it would have gotten on my pc, unless it somehow was stored in my router or something. I was using comodo firewall when I got the virus a few days ago. This time I just stuck with Windows Firewall because I thought it might have blocked something that was important (I did that once before and had a rough time fixing it). If you have any advice about what additional security software I should run it would be great.