new mobo causing jitters?

[[H]unter]

Got a new motherboard replaced in my Dell M1330.
Popped the harddrive back in.
Booted up eventually.
But the whole OS is now jittering. Sounds jitters (skips and repeats then resumes...) so does video and even the mouse movements are effected.

Tried resinstalling drivers. Nothing changed.

Is there something I should check. Is it a hardware issue?
my next step is to reinstall from scratch, but I would rather avoid this if I don't have to.

Thanks for all the input!

 

[[H]unter]

Went into Bios, Rechecked all settings and presto.
All good.