Browser redirect??

Hi - both my browsers chrome and IE7 constantly redirect me to blank page sites such as s.7addthis.com static.facbook, static.twitter etc, etc,

So far I've tried entering safe mode and checking msconfig. Resetting browser defaults and LAN settings and I've gone through a disk clean up.

I have also tried the following software.
TDSSkiller
ADWcleaner
Malwarebytes

and I am running avast.

I am not brilliantly computer literate and so I thank anyone in advance that can help me put this right....

Browser redirect??