XMP is not support in every RAM module even if it is compatible with the motherboard.. I've seen few Kingston hyper-x RAM's supporting them.. Anyway, as suggested by Lmeow, you need to clear your CMOS as the first step.. Download and install CPU-Z.. It'll give you information regarding your system hardware.. Check for information regarding memory.. Then if required, you can change it in your BIOS..
P.S. - How did your friend convinced you about your RAM's operating at lower speed than rated.?