why can’t i download any malware scanners?

i have been infected with the trojan-keylogger.WIN32.fung virus and personal defende ads have popped up on my computer even after installation. it has even crashed my coputer once or twice. so i decided to try and download some malware scanners such as spyware hunter file assassin and others. however every time i try to download these scanners the computer says that my settings won’t allow me to download these files, so what settings should i change, in order to install these malware removers so tat i can be rid of these ads once and for all?

To answer your question you should enter Safe Mode with Networking

http://www.computerhope.com/issues/chsafe.htm

I would recommend
Download and update Malwarebytes AntiMalware

http://www.download.com/Malwarebytes-Anti-Malware/3000-8022_4-10804572.html

and
SuperAntiSpyware

http://www.superantispyware.com/

Also I would recommend scanning in Safe Mode

In some cases you need system restore off while cleaning

http://www.pchell.com/virus/systemrestore.shtml