power problem can i use 2 power supply's

hey guys i recently upgraded my graphic card to a msi Radeon hd 7970 lightning 2gb and the power supply ive got right now can't handle it because it only has 1x8 pin and the graphics card has to have 2 x 8 pin. so i thought lets power it using a external power supply i've got one that has 2x8 pin but the question to you guys is: is that save to do or is that save for my new graphics card ????

@dennierr:

What PSU do you have installed and whats the spare one?

Either buy adapter or brand new PSU.

I'd go with brand new PSU since they're dirt cheap and all you need is 500Watts at top - they're sold for 20-30$

EVGA 500B - $35

Corsair CX500 - $30

uuh my current psu is the ms-tech 650 watt val and the spare one is a cm 550 watt but the recommended psu for my new graphics card is 650 watt but i was thinking that i connect the green wire to the green wire on my psu thats connected to my motherboard making the spare psu only turn on when my system is on but will that help ??

WUT? 1st of all don't mind the "recommended" PSU wattage for any GPU, this is to make sure you have enough headroom for connecting 12 fans, 4 dvds and 8 HDDs and even that is too much for all that setup.

2nd you can't connect 2 PSUs to make 1 system run.

i wanna do something like this http://www.thermaltake.co.nz/product/Power/PurePower/w0099/w0099.html only then with a bigger psu 1 of 550watt

You can clearly see it's a mess in the picture in terms of cable management, keep your current PSUs for a friend of another computer in the future such as media center, and buy yourself a proper PSU or get yourself some special adapter if such thing exists (I know of 6 pin to 8 pin adapter)

Next time you buy something make sure everything you current have is compatible

Yes you can with this

http://www.amazon.com/Vantacor-Dual-Adapter-Cable-2-way/dp/B00DL3L2J6/ref=sr_1_1?ie=UTF8&qid=1418479959&sr=8-1&keywords=dual+power+supply+adapter

ok guys i got my friends 550 watt now and my system can run on it i used my 1st psu for the fans though. but thnx for your help guys XD

Yes, you can. It's just electricity and it's been done before.

That is overkill to use a PSU just for fans, but whatever works best for you I guess. The 550W can handle the card and your fans without the need for additional power.