Firstly, Do NOT download and install any more anti-virus programs unless you completely un-install any current anti-virus program that you may have.
The use of 2 anti-virus programs at the same time can cause major conflicts. The 2 scanning engines will fight each other to scan every file that you read, write or execute which can cause a slowdown. For the same reason, using 2 A-Vs can cause you to have less protection from the various malware, not more.
(Using an anti-spyware with an anti-virus is good, however and is recommended)
A much better solution, right now when your computer is apparently infected, is the use of on-line scanners.
Run both of these on-line scans. Both are free and excellent at detecting and removing malware free of charge. There is no need to un-install any of your current protections (if you have any) before using these.
1. Scan for virus, worms, dialers, etc. and remove (free online scan, no downloaded program) with BitDefender's Online Scanner. Press "Scan now" on the left.
http://www.bitdefender.com/
2. Scan for trojans, adware, cookies, and spyware and remove (free online scan, no downloaded program) with Ewido Online Scanner ( now known as AVG Anti-Spyware). This is NOT the same as AVG Anti-Virus. Press "Scan your computer now online and clean it for free!" on the left.
http://www.ewido.net/en/
These scans will take quite a bit of time. The time is necessary to clean-up an infected computer.
__________________
Someone has suggested that you use SmitfraudFix. Don't bother! SmitFraudFix is a specialised removal tool that removes exactly 1 (one) type of infection. It will do nothing to remove the other roughly 999,999 types of computer infection.....As they say, "a little knowledge is a dangerous thing".
Good luck.