Thanks for the detailed replies!
@gchurch & dan.wildcat:
It's nice to hear from techs who obviously have troubleshooting experience. I had just written a detailed reply about all the steps I had tried while troubleshooting this system but when I submitted the post it did not show up. I'm going to try once more. It started as a call from a client with and infected workstation. I did some scans with Kaspersky Virus Removal Tool and MalwareBytes and found It was a nasty rootkit and a couple other malware/virus infections. The users files were on a server so I went with a clean reload. After reloading I changed the advanced system properties like I normally do so it would not automatically reboot on errors and it would save the minidump file. Everything was looking good after installing all the Windows updates and loading their business software and then the random reboots started. I checked the ram with Windows Memory Diagnostics and the hard drive with Spinrite and both passed. I also updated the bios and all hardware drivers and the reboots persisted with no discernible pattern and nothing showing in event viewer. I had already opened the case to dust it out and check the fans and cables. To make a long story short I finally removed the hard drive bay and sure enough I found a couple caps on the motherboard that were bulging at the top, one even had some residue from where it had leaked. Now I just have to check on the cost of a replacement board if it's available and decide if it's even worth replacing. It's one of those Dell Optiplex systems that in my opinion have a horrible case design that makes then prone to overheating.
