Trojan Horses PSW.Generic7.APIQ, Win32, etc.

Since 10/30, apparently from a (non-porn) website, my PC's been infected by multiple Trojan Horses, viruses, and Malware: most recently, PSW.Generic7.APIQ; previously, Win32/Cryptor, Generic14.BLRH, Vundo II and IH, the virus Packed.Hidden, and apparently Win32.agent.pz and Win32.ZBot (although these have shown up only in SpyBot 1.6.2 scans, not in AVG Free 8.5 scans like all the others). Also maybe svchost.exe (appeared a couple of times at startup) and, always at startup now, RUNDLL window reading Error loading kujejato.dll. AVG allegedly moves infections to Virus Vault and I delete them; SpyBot keeps turning up the two Win32 TH and Malware (4 entries in all), even though I "fix selected problems" (and they're marked as fixed, with green check marks) and even Purge supposed backups of them that turn up in Recovery at the end of each scan. (After some SpyBot scans, a Spybot SD.exe - Application Error also appears. In each case, when one of these windows appears--RUNDLL and .exe Application Error--I close window, with the x at upper right, rather than clicking on OK.)