Ok, that didn't find much, mostly cookies. We'll clean the log up and see if that helps.
Run Hijackthis and select "Do a system scan only", place a check by the following entries.
R3 - Default URLSearchHook is missing
O9 - Extra button: Erotic - {8E65B894-C2E9-11D5-BCD3-00E018987507} - C:\SEXO155gb\SEXO155gb.exe (file missing)
O9 - Extra button: (no name) - {CD67F990-D8E9-11d2-98FE-00C0F0318AFE} - (no file)
O16 - DPF: {91413D86-9F27-402C-B5E3-DEBDD122C339} - http://content2.netvenda.com/sites/g.../uk/games4.cab
O16 - DPF: {91433D86-9F27-402C-B5E3-DEBDD122C339} - http://content2.netvenda.com/sites/g.../gb/games4.cab
O23 - Service: .NET Framework Service (.NET Connection Service) - Unknown owner - C:\WINDOWS\svchost.exe (file missing)
Close all open windows and browsers, and hit "Fix Checked".
Hit Start >Run, type services.msc.
Scroll down until you find the service
.NET Framework Service, and double-click on it.
Hit "Stop" and change the "Startup Type" to "Disabled".
Hit "Apply", then "Ok".
Then run HijackThis and click Config -> Misc Tools -> Delete an NT service. In the Delete window, type
.NET Connection Service and press OK. OK any prompts, close HijackThis.
Delete this file (be careful, it
must be in the Windows folder, not Windows\System32).
C:\WINDOWS\
svchost.exe
Then restart the computer and post a new Hijackthis log.