Please help me - keep getting virus warnings

If anyway can help me with this i will be eternally grateful.
I bought a Toshiba laptop about a month ago and within 2 weeks it said i had a virus and trojans and it wouldn't let me do anything with it until i downloaded antivirus software, which i had to pay for!
Anyway, i paid for the antivirus and everything was fine until tonight when it says i have trojans and viruses again so i tried to look for the antivirus software that i downloaded the other week and cant find it anywhere. I have now downloaded Avast for free, but Windows Protection Suite is still telling me i have a virus and to pay again to get it removed. Does anyone know what i can do. Do i still have the viruses or is this computer safe to use?
Any help will be gratefully received.

Hello,

Read this: http://www.geekpolice.net/-t3821.htm

And post your HijackThis log here.