Well...how about a little more info on this system
System manufacturer and model? How much RAM installed? How large is C: partition? How much free space currently on C:?
FWIW: AVG 8.5 is quite old, IMO. BSODs can be caused by many things, including lack of proper maintenance, damaged files, and hardware problems.
Download/install BlueScreenView, http://www.nirsoft.net/utils/blue_screen_view.html
Double-click BlueScreenView.exe file.
When scanning is done, Edit/Select All...then File/Save Selected Items. Save the report as BSOD.txt. If the reported date for errors is not in chronological order (most recent at top), then you may want to sort that column to make it so...before saving the file.
Open BSOD.txt in Notepad, copy all content, and paste it into your next reply.
General info on slow computers: Slow Computer-browser Check Here First; It May Not Be Malware - http://www.bleepingcomputer.com/forums/t/87058/slow-computerbrowser-check-here-first;-it-may-not-be-malware/