I thought I blew out my new Thinkboy over the weekend, turns out I didn't realize that a mini-ITX board needs a 12 volt 5 amp power supply but a 10 AMP fuse. I only gathered this information by scouring Japanese mini-ITX support groups.
This isn't the first time I have worried I have blown everything up and it turned out to be a fuse. This is a good reason to stock a lot of fuses.
Anyway, in the process of reinstalling Windows 2000 Advanced Terminal Server on a compact flash inside 200 megabytes of storage space. It runs really, really fast. I was in the middle of creating another partition on a backup CF when all of a sudden the system just turned off. The 10 AMP fuse will give you enough protection but won't blow until it really needs to. A 5 AMP fuse will often blow at 5 AMPs, meaning normal operation of the mini-ITX will blow the fuse.
Took about two hours to locate this problem. You can see why this kind of thing takes a lot of patience and time to get right. In my setup, it was the first time I tried to drive a second storage device off IDE 44 PIN power, which apparently pushed the 5 AMP fuse to commit hari-kari.