Cpu problem

That will depend on the Graphics card as well. It is not the best CPU but with a good GPU it will be able to game, not necessary on highest settings though.

if i buy a core 2 duo e7500 and gts 450 so will i be able to play high end games on their highest settings games like
crysis or call of duty black oops.
i also have 2gb ddr3 ram

That combination will handle most everything well at low resolution. It will though struggle with Crysis http://www.techpowerup.com/reviews/MSI/GeForce_GTS_450_...
2gb ram is OK if you have a 32bit OS if 64 bit 4GB is the recommended min.

I would get more ram 2 gigs is a joke now days. Get a good cooler with your cpu and oc it.

2GB DDR2-1066 [have one dead stick, lost packaging=(] has yet to hurt my performance w/ 4890 crossfire on 32bit 7.

Agreed however, that 4GB is the norm and best price/performance these days, when shopping for a new set.

i want to play those games on high what should i upgrade cpu or gpu

You'd need to go up to a quad core and a gtx 580 I think. Alot depends on the resilution you'll be gaming at and as you will see from the charts, even an overc locked 580 struggles with crysis at 2560x1600. You may have to go SLI if you want better graphics than that.
http://www.tomshardware.com/reviews/geforce-gtx-560-ti-...

thanks for your replay ,but
i am just gonna play those games on standard resilution 1024x768. I think i will be able those games on high

@ that resolution you will be fine with E7500 and GTS450!

one more thing there are two processors that i am looking forward to and might buy in the future. One is core i5 760 and second is amd phenom ii x4 940. Which one is better

I5 760 http://www.anandtech.com/bench/Product/80?vs=191

I5 without a doubt. Phenom II if your budget is tight.

one more thing i need to ask
for this system i am buying cooler master extreme power 600w psu or might buy corsiar 430w psu. The cooler master has 18 amps and the corsiar have 28 amps. What should i go for

I would get the Corsair although it is their budget PSU it is more reliable brand than CM.

will it be able to handle this rig
core 2 duo e7500
2gb ram ddr3
gts 450
intel dg41wv
cooler master 370

Yes it will handle that fine.

but if i go for a dual core e5700 than my cpu will bottelneck or not

you can visit some cpu sites......