windows keeps freezing up

[MJ1000]

Hi folks,

I'm new to this forum. My pc is about 1 yr old and starting about 1 month ago, it would freeze up late in the afternoon.(every afternoon). Clicking on icons gave me the message that I did not have privileges to open this file. A hard reboot and the pc behaves fine for the rest of the day. I ran multiple antivirus/antispyware programs (including hijackit) - nothing. I had the pc checked by the service people who found a conflict between my main drive and a second backup drive. This latter was replaced, and vista reinstalled. The pc ran fine for one week, and is now freezing again late in the day. Also windows explorer restarts quite often. Does this make any sense ?

Thanks for any input,
Michael