I just checked out some information on the net, mainly dealing with upgrading and or replacing the video graphics card on a Dell Studio 1749. Dell officially reports that upgrading video on the Studio 1749 is a "no go"! Some other various source material I saw also backs up what Dell says and they to report that upgrading the Studio 1749 graphics is "not possible"!
For what I did see on Dell's web site, in regards to your computers system spec's, why would you want to change out the video solution that came with the computer? If your system has the same spec's as the Studio 1749 I saw on paper, it's a integrated 1GB ATI Mobility Radeon™ HD 5730 Graphics Card, why change it? Or is this 1749 I saw a "high end" system and maybe you have one a couple ladder rungs down! Maybe your looking at a cheaper Intel integrated graphics set, what ever the case may be, all the sources I saw say "no".