Can the Dell Optiplex 755 use the GT 630 2GB

The Small Form Factor Dell OptiPlex 755 has a low profile PCI Express x16 slot. The GPU you linked will not fit as it is not a low profile card. Make sure you pick one that has a low profile bracket and you shouldn't have a problem.
 
While you would probably need the optional riser card in order to install that graphics card. It appears you could do it. I agree with skit75's assessment in that this would barely be considered an entry level gaming system. Unfortunately, there isn't much more you could do with it given it's 280 watt power supply.

-Wolf sends

System Specs
Tech Specs
Desktop Model.
 
You also need to take into consideration that your machine only has a 275watt power supply. But as long as the card says low profile, it should fit.
 


It sure is.... good catch. That card will fit in there physically with a right-angle extender board. Being a GT 630 (lower power) model, it will probably run fine also.

cheers
 
The one pictured in the Newegg ad is a SFF Optiplex 755

Small Form Factor

Number of Bays
1 internal 3.5", 1 external 3.5", 1 external 5.25"

Dimensions
H: 12.45" W: 3.65" D: 13.4
H: 31.63cm W: 9.26cm D: 34cm

Slots
1 low-profile PCI
-(H: 2.5" X L: 6.6")
1 low-profile PCIe x16 graphics
-(H: 2.5" X L: 6.6")

Power Supply
275W

It will still require the riser card. The bracket should be OK though
 
I posted the same link (system specs). If you'll note, the Small Form Factor and the Ultra Small Form Factor systems (the two on the right) both have slim-line optical drives. There is no space for a full sized optical drive in either small form factor system.

-Wolf sends
 


In "The number of Bays" Dell lists a single 5.25" External slot just like the one pictured on Newegg has. Dell must be using stock photos for the line-up picture because they are visually inaccurate according to the Technical Specifications of the SFF 755.
 
Your system is the Slimline Desktop which only provides 25 watts of power to the PCI-Express slot.
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Using a higher rated card, while may initially work, will run the risk of blowing out the proprietary 280 watt power supply.

I would suggest this one instead to be safe
ASUS Radeon HD 6450 Low Profile http://www.newegg.com/Product/Product.aspx?Item=N82E16814121439.

Or if you want to push it, this would be the fastest card that should theoretically work but pulls 55 watts of power.
PowerColor Radeon HD 7750 Low Profile http://www.newegg.com/Product/Product.aspx?Item=N82E16814131509.

You will also probably need the PCI Express Riser card.
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