Need some help with Trojan Remover

Recently, my computer has been opening random Internet Explorer windows and so I thought I had a couple trojans and got Trojan Remover. It seemed to be working fine but half way through the scan, it just stopped. When I tried to open it again, I get a message saying Windows cannot access the specified device, path, or file. You may not have the appropriate permission to access the item. I then tried to start my antivirus program (Avast! antivirus) and it also stopped suddenly after a couple seconds and I'm now getting the same message with it. I'm running Vista Home Premium, and I'm the admin so I don't know why I wouldn't have permission. I've already done a system restore but the problem remains. If anyone has any ideas, I could use them. Thanks in advance.

 

Just an update. I've downloaded Avenger, MGtools, FixAVP, SeDebug-Restore, and RegSearch and I can't run any of them and now my explorer.exe file isn't working properly. My desktop icons just have a name and no actual icon above it and my background is just a black screen.

 

Thanks for the advice. I was able to fix the problem, but it took quite a bit of time. I had to basically do a factory restore and then re-install Vista. I discovered that the virus had infected the drivers for my OS and soon it would not start up the computer. A certain file was missing from system32. Fortunately, I was able to boot up from a USB flash drive with XP and some anti virus programs on it and I transferred any uninfected files for an external hard drive. So my problem has been fixed and this thread can be closed. Thanks.