Sorry about your server. I'm glad that it's over. I've heard of a similar situation with McCafee and Norton, but it didn't cause restarts.
Even though your IT guy deemed it a software issue, these restarts seem more like a hardware issue. Even though it may seem like the power supply is the problem, I've seen this plenty of times with failed hard drives which is probably why your first guy suspected the power supply. Most redundant PSUs/Servers in general have a WatchDog line, which basically restarts the server if it hangs/stops responding. The watch dog line is directly connected to the power switch. So if the os were to hang/crash or a hard drive were to fail or stop responding for some reason, the server would restart to maintain uptime or in the case of a failed hard drive, continually restart. Which makes it seem like a power supply issue. These restarts would be occasional in the beginning and as the corruption spreads throughout the hard drive, the restarts become more frequent. Just a thought. I haven't seen the logs so I can't make an informed decision like your IT guy.
A couple of questions:
1. Do you have a hardware RAID controller? Are you using software RAID?
2. Did you run a disk utility from the drive manufacturer? E.g. Seatools for Seagate
3. Do you have an eSATA/USB 3.0 backup drive? Copying 35GB on an eSATA/USB drive would take about 5-10 minutes which is why Bert and I strongly recommend them over USB 2.0
4. What do you mean 8 hard drives as one big hard drive? Did you do a software RAID 0?!
Virtualization is a good idea assuming you have no hardware devices attached. I have a fax board, that's my main reason for not virtualizing. Be sure to take that into consideration. There's ways around it of course. Use a Hyper V Parent with Fax Services and join into the Hyper V Child SBS 2011. Or a separate physical fax server or UpDox or PaperPort. Whatever floats your boat.