In your initial post you are telling us that you are using Windowx XP Professional SP2, now you mentioned that you are using Home Edition.

.S. I almost forgot - I'm using Home Edition

Have you tried downloading Total Commander 6.50 from some other source ? Are you logged in Windows under account with administrator rights ? As I said before, I never had any of those problems with installing other programs while avast! is running. Same thing Igor tried, and nothing… try installing it using some other installation package.

Cheers !