Ok I have a 420 watt power supply, can I overclock this guy (amd 5000+ black edition) just a little without hurting anything?

It depends. There are other components that draw power, like graphics card and harddrives.

well i have 2 8500gt 512s, and 2 gb pc 6400 ram. 320 gb harddrive.

Asus M2N SLI NVIDIA nForce 560 SLI MoBo

Wat psu do you have and what is the amps on the +12v line?

hmm, sorry I'm a noob atm. Couldn't find that out yet. The pc will be here in less than an hour I'll get back to you on that. BTW I was only going to OC this guy to 3.1 ghz

If it's a prebuilt PC from a large company, like HP or Dell, the motherboard may not allow oc.

its from cyberpower so I know i can OC it

 
Just because its from Cyberpower doesn't mean it can be overclocked. However, if that 420 wt PSU is one of the standard PSUs, especially an Aspire/ Apevia PSU, then you will need a better PSU before you do much of anything. Overclocking involves a lot of things, like motherboard selection and type of ram, as well as the CPU.

We need to know the specifications of the PSU and other components.
 
Just wondering OP, why did you opt for two 8500gt's? For four monitors I hope and not for games? D:

I know that you'll be able to overclock it, a friend has a Cyberpower and he has it overclocked. But I'm not sure about the power supply, that's pretty low.

Well it looks like I cant OC it very much got the 5000+ to 2.8 ghz... good enough. Above that and I get a error message from Prime95. Everything seems to be stable been torture testing it for quite some time now.
 
I'm going to invest in a 900 watt PSU so then i can really crank this baby up Oh and the dual videos were part of a very cheap package deal... It was like 60 bucks for the two and for just one you'd basicly be losing money.

900wats!? You really don't need anything more than 650 unless your going SLI with a 9800GTX or higher.

 
 
You should ask for advice before going any further. SLi 8500 GT's  cant use the 512 mb and still give you crap performance. i would get your money back if i could, if you have enough to pay for a 900w psu get a better card. a 9600GT is very good performance for its price, or a 8800GT, both would crush SLi 8500GTs, and just a high quality PSU (corsair) would let you OC fine.