AMD Phenom II X4 965

Windows sometimes has problems.

What does a program like CPU-Z say?

Well i don't know, where i can see, it just says 866 MHZ (at CPU-Z) ... at core speed, but it sometimes it changes, like when i load a program it goes at 3909

I have the same chip, and had the same board also.

If you have cool n quiet enabled in BIOS, it can slow down the clock when the CPU is not under load. It can also do this if you have the windows power options set to anything other than "maximum performance", with the advanced options set with the processor cooling set to "active". Passive will slow the CPU down when not being loaded as well. Given, neither of these are bad things necessarily, other than making it harder to find a stable OC setting when trying to tune it in. It sounds like your actual overclock is just fine- you just won't see it unless you change the settings (which really is optional), or unless you confirm with something like OCCT, which will load the CPU to 100% while giving temp and clock speeds.

i concur, disable cool and quiet in bios and change your power settings to performance. btw, thats a good overclock