This is a common symptom of the Zero Access infection but can also be caused by some anti-viruses (AVG is the most common).
For Zero Access your best bet is Combofix. You will have to download it on a friend's PC (Note the caveat about turning off your anti-virus while downloading or moving Combofix. Make sure you do it on both PCs) and put it on a USB drive or on a CD then move it to the desktop of the sick PC. Might as well also get OTL
http://www.geekstogo...timers-list-it/
and FRST
http://www.bleepingc...very-scan-tool/
just in case Combofix won't run.
ComboFix
:!: It must be saved to your desktop, do not run it from your browser:!:
:!: Disable your Antivirus software when downloading or running Combofix. If it has Script Blocking features, please disable these as well. See:
http://www.bleepingc...opic114351.html
Download and Save this file -- to your Desktop -- from either of these two sources:
http://download.blee...Bs/ComboFix.exe
http://subs.geekstogo.com/ComboFix.exe
Vista/Win 7/8 =>Rightclick on ComboFix and select Run As Administrator to start the program.
XP => Double click to start the program.
* :!: Important: Have no other programs running. Your Task Bar should be clear of any program entries including your Browser.
* A window may open with a series of Disclaimers. Accept the Disclaimers to start the fix.
A caution - Do not run Combofix more than once. Do not touch your mouse/keyboard until the scan has completed, as this may cause the process to stall or your computer to lock. The scan will temporarily disable your desktop, and if interrupted may leave your desktop disabled. If this occurs, please reboot to restore the desktop. Even when ComboFix appears to be doing nothing, look at your Drive light. If it is flashing, Combofix is still at work. If you do not get a log then run Combofix a second time.
I'll need to see that in your reply.
If it's the latter problem (Combofix runs fine but doesn't help) and you have Firefox then you can use a work around:
Type in:
about:config
and hit Enter
then scroll down until you find
browser.download.manager.scanWhenDone
then right click on it and Toggle. Close and reopen Firefox and try to download something in Firefox.
If you have Chrome then usually the following will get it to work:
Copy the lines between the stars (but not the stars):
****************
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Attachments]
"ScanWithAntiVirus"=dword:00000001
****************
Open notepad and paste the above into it. Verify that you have it all then File, Save As, (to your desktop) "NoScan.reg" OK (Make sure you includes the quotes around the file name)
Close notepad. Right click on NoScan.reg and select Merge. Allow it to merge. (If you don't see the Merge option you probably left off the quotes and notepad tacked on .txt)
Ron