What you CAN do is check the clockgenerator on the motherboard, get the part number and then check out a program called CPUFSB (google should take you straight to it) to see if it supports it.
I did this with a Dell Optiplex GX100 recently.
A lot of the big manufacturers use clockgenerators that don't connect to the SMBUS, which is how a lot of the software fsb programs (like clockgen and cpufsb) read and write to the clockgenerator. This is why most of the software fsb utilities also don't work.