To my surprise no$gba 2.6a runs perfectly, or even better than it did on vista, but i have some issues with the cheats that i've been longin to ask help for, first i am unable to add game shark or action replay, and code breaker has issues with tales of phantasia (U). Running on a laptop with Win7 ultimate, and to be specific the issue is that some CB codes show up as ? but then when i click on the master code and click ok the only code can be selected, if i have more than a single code it goes ? and i doubt it's a code issue as i have several for the 3 GBA FE's and the hacks.
Try using the No$zoomer add on. Using it, you can use R4.DAT file for your cheating use. Save you from the need to input code manually. Although this is the first time I hear this problem, since I've been using Windows 7 Ultimate myself and doesn't have any problem with no$gba cheating.