Talha096,

At the link below are the specs to run the GT610.

Nvidia GT610 Specs

GDDR5 GT1030 cards from Gigabyte fit and work fine.

https://www.amazon.com/GIGABYTE-GeForce-GV-N1030D5-2GL-Computer-Graphics/dp/B071DY2VJR/

I know this is post is 6 months old but I did a lot of looking and due to height and width limits of 755 DT the maximum capacity card that I could find (and they're getting scarce) if you want to be able to close the cover is the AMD Radeon HD 6450 LOW PROFILE, SINGLE WIDTH with DVI and Display Port interface ONLY. A very short, very thin card. I used a DVI to HDMI cable to a 24" 720p TV / Monitor, bit you can go up to 32" 1080p for less than $120 now. The drivers will install as 7000 series but work fine. This is still a DDR3 1GB card. Hope you figured it out. I also recommend a Q9650 CPU (not QX), A22 BIOS, 8GB of the fastest DDR2 RAM you can find and an SSD. With a couple hundred bucks and some BIOS and Registry tweaking you'll be maxed out but still have great performance for surfing, video and very light gaming.

Thanks. It operates at 34W. Costs 6 times as much as the 6450 too.