Did you buy this pc prebuilt?
Try updating bios and try again.
If you come in bios you have to set the oc option to manual to be able to change the voltage.
Did you oc to 3.7ghz without changing voltage? nice
Go to the advanced tab, jumperfree configuration, then AI overclocking, change it to manual. Then you should see all the options to change fsb, voltage and other things.