You can use avast! uninstall utility:
http://www.avast.com/i_idt_1336.html. If you can't uninstall avast through Control Panel, you can download the uninstall utility called AvClear or AvClear4 (depending on your avast! version). More information
here.
So any help you can give with this lot will be gratefully received.
After booting, maybe you can try a clean avast installation

Well, the reducing from 59 to 6 days is due to TRIAL version registration key.
To avoid piracy, 2nd installation of the trail version goes from 59 to 6 days of validity.
Are you using the correct Registration key?