what motherboard does this dell studio 9000/435t comes with

[lepelletier]

I know it is a legacy platform. Not uefi so it is very limited for upgrading graphic card...
Will the evga 750gtx fit?

 

[cin19]

If the dell is the Dell Studio XPS 9000, it has the lga1366 X58 chipset MB, it has the pcie2.0X16, so the gtx750 will fit. Because it came with 475W PSU, so you can use it with the gtx750, just check your evga gtx750 need the pice power cable or not. If the gpu does not that cable you may just plug it in.

 

[lepelletier]

If the dell is the Dell Studio XPS 9000, it has the lga1366 X58 chipset MB, it has the pcie2.0X16, so the gtx750 will fit. Because it came with 475W PSU, so you can use it with the gtx750, just check your evga gtx750 need the pice power cable or not. If the gpu does not that cable you may just plug it in.

Thank you so very much for your prompt and nice answer cin19!!! I appreciate knowing what kind of motherboard I have. Dell would not even tell me!!!
However...re the graphic card EVGA 750 GTX...It might fit in size inside the computer but it will absolutely not work on this Dell since the motherboard platform is Legacy not UEFI !!! It might initially work for a bit but will keep crashing. In addition This Dell will only accept PCI Express 2.0.....Nothing higher/newer...EVGA and other computer parts store absolutely confirmed that!!!
So I just opted for the EVGS GeForce 2GB-P4-2643-KR...THE HIGEST GRADE GRAPHIC CARD WHICH WILL FIT THIS COMPUTER. NOT EVEN A GEFORCE 660 GTX WILL WORK!!!

Same thing for Windows 10....this computer kept crashing after a few days of windows 10 install since windows 10 needs a UEFI Platform motherboard .Windows 10 will not work on Legacy platform motherboard, which is why Dell does not offer any drivers for the upgrade to Windows 10 from windows 7. It will not work...it does for a few days, then it keeps crashing...

 

[cin19]

You may check the BIOS to see what version you had, also check the dell to see they does provide the BIOS that comes out after 2010, if they do then update the BIOS, and you should use other GPU to do it. After that switch to the gtx750. How to check the BIOS http://www.wikihow.com/Check-BIOS-Version

Also you may try use the DDU to uninstall the GPU driver, then reinstall the nvidia gpu driver from nvidia site.
DDU http://www.guru3d.com/files-details/display-driver-uninstaller-download.html
And you may open the case double check the PSU to see it is the 475W one or something else. And do your gtx750 have the 6-pin pcie power connector? Because some of model have it

The win10 can work on the legacy platform motherboard, as long as your PC meets the requirement. I used the win10 insider version on the lga 775 MB ( evga nForce 750i MB ), and I still run it time to time.
If you run the win10 that upgraded from the win7, you can try to do the clean reinstall the win10, sometime that will solve the unknown problem. If you want to try, here is how to http://answers.microsoft.com/en-us/insider/wiki/insider_wintp-insider_install/how-to-do-a-clean-install-of-windows-10/aef0ae63-2117-41ee-a8ea-4a3181625b08