[Sweeper]

I built a pc for a friend for his company. (Auto shop)
Anyway, every other week it seems he will shut the computer off at night and when he goes to turn it on the next morning it boots up in Safe Mode? Then he has to shut it off and restart and it will boot up normally. I have taken a look at it and tried a few things but to no avail..................... He is now getting rather annoyed having to restart it randomly and isn't happy about the Safe Mode screen being it's a new system. 3 weeks old.
System specs:
MSI 845 G-Max (MS-6580)
P4 2.4GHz (533)
1 x 512 Generic PC2100 DDR
80 GB WD 8mb Cache HD
MSI - GF2 400 (can't remember the exact card)
10/100 NIC (generic)
56K PCI Modem (generic)
Sound Blaster Live 5:1
300w PSU
Mid Tower Case
Room temp when running 72F
Room temp when PC is off 60F
CPU Temp: 45c
MB Temp:31c

Any suggestions? The only applications he runs are Quickbooks and Mitchell on Demand. And his normal office software.

Thanks