Nearly every morning when we switch on the main work pc, it freezes before loading Windows. Occasionally some mornings it doesn't do it. Other times, we have to power it on and off some 5 times before it decides to work properly! This has been going on for weeks now.
Usually it freezes on the password screen, either before or after inputting the password.
Once Windows loads, the computer works perfectly. It even crunches all the time at 100%.
I've tried several things now:
- memtest
- scanning for viruses (including with malwarebytes).
- repair using the Win 7 disk.
- sfc /scannow which found everything ok.
- ccleaner.
- the full version of Registry Mechanic.
(I wouldn't want to do a fresh Win 7 install because then we'd have to re-install the accounting software as well and it'll be expensive since for security reasons the seller doesn't distribute diskettes and passwords..

)
Here are its system specs:
Q9400
Asus P5KPL-AM SE
1 x 2048MB Supertalent DDR2
Onboard graphics
Win 7 x86 SP1
Suggestions?