Most likely four modules (I've not seen motherboards with 5 memory sockets).
If you wanna know if the RAM is the problem, you have to know how much total memory is installed through the four modules, and compare that number to what Windows is reporting.
Example: if the four RAM modules are 128MB each, then your total memory should be 128MB * 4 = 512MB. Now, if Windows only reports 384MB, then it's probable one of the modules is fried.