To be honest, much as I'm a huge Linux advocate, I really don't think CruelAndUnusualParenting's suggestion is necessary yet.
It's totally normal for even the most "wimpy" of infections to prevent access to known anti-virus and anti-malware websites, and to prevent execution of the most popular security tools.
All that is generally required is to download the tools of choice on a clean machine, rename them (a truely "randomname.exe" is actually better than one that still has the first few letters the same as the program you wish to run) and burn them to a cd or use a USB flash drive to get them over to the PC you're trying to fix.
Nannynick's suggestion of combofix is a good one, but that wouldn't be my first line of attack if I were advising someone how to clean their own machine, as it isn't a beginner's tool, imho.
Start with downloading rkill from download.bleepingcomputer.com/grinler/rkill.com and Malwarebytes: download.bleepingcomputer.com/malwarebytes/mbam-setup.exe (as recommended by CruelAndUnusualParenting, earlier - an excellent free Antimalware program that I cannot recommend highly enough!) and then boot into safe mode (with networking).
Run rkill first and then, without rebooting, install malwarebytes and perform an update and a full scan.
If malwarebytes won't run, get back to me, as rkill should kill most known malicious processes, but certain infections can still require you to rename the malwarebytes core executable, or they may even replace it, requiring you to run another copy of it that you've downloaded separately and renamed.
Let us know how you get on, and if/when you get Malwarebytes to run, allow it to remove everything it finds and reboot into normal (not safe mode) if it says it needs to reboot to complete the cleaning process.
You should then be well on the way to a clean PC, but don't feel that you are completely done yet, as Malwarebytes is definitely one of the very best tools but it can still miss a few things that will be caught by various others that I would recommend running later...
It all sounds pretty complicated but it's not that bad really - honest!