rattling

Heya iv recently purchaced a Clio F1 (3 weeks ago :( ) love the car but iv broke it already... the symptoms are when the car is tarted it sounds rattly like a belt squeeking... but not like the common car squeek if you know what i mean... it stalled twice pulling away on way home from work...

About a fortnight ago my car started rattling, it does it in every gear at 2,500 RPM roughly. It doesn't do it while not moving. Hence this is proving tricky to find the problem. It is smooth up until these revs then sounds like something is loose but only lasts for about 200RPM at max between...