Avast also has update files that can be downloaded and installed separately. These come in the form of self-extracting executables. Even digit was providing this a few times...
AVG Free version does not remove viruses, but only detects them AFAIK... Go for Avast... I have found it to be better than AVG. I used AVG for a long time and when I changed to Avast, I found it much better. AVG is lighter in terms of resources, but in every other department, I think Avast is better...
Not sure what you mean by Antihack software... Do you mean Firewall (try Kerio Personal Firewall or Zone Alarm Personal), Anti-spyware (try Spybot Search and Destroy and Lavasoft Adaware) or perhaps other specific software such as RootkitReveal from SysInternals, HijackThis, etc.?
Arun