Everything I've tried ran great on Windows 7, I literally install hundreds of programs and games on my computer which Windows 7 ran as good or better than Vista.
I would recommend Vista/Windows 7 x64 just because they include native multi-core support where as with XP it wasn't native and there were issues with multi-core. It's one of the reasons for AMD's dual core optimizer on XP, which is not needed with Vista/Windows 7. I'd also recommend Vista/Seven x64 over XP x64 as XP x64 is just Windows server 2003 wrapped in XP's fisher price GUI, Vista is the first consumer Microsoft OS to support x86-64 natively thus solving a lot of the compatibility issues that were present with XP x64 (Referring to having to constantly edit .msi installers for games and other applications).
If your specifications are decent enough to handle the small overhead of Vista, I'd recommend installing/using Vista x64. Also I would suggest Windows 7 x64 as a second choice, it is able to run a lot more efficiently on older hardware than Vista does.
Both are great choices for Dolphin, both can run the x86, x64, x86 JITIL, and x64 JITIL builds of Dolphin just fine.
I would recommend Vista/Windows 7 x64 just because they include native multi-core support where as with XP it wasn't native and there were issues with multi-core. It's one of the reasons for AMD's dual core optimizer on XP, which is not needed with Vista/Windows 7. I'd also recommend Vista/Seven x64 over XP x64 as XP x64 is just Windows server 2003 wrapped in XP's fisher price GUI, Vista is the first consumer Microsoft OS to support x86-64 natively thus solving a lot of the compatibility issues that were present with XP x64 (Referring to having to constantly edit .msi installers for games and other applications).
If your specifications are decent enough to handle the small overhead of Vista, I'd recommend installing/using Vista x64. Also I would suggest Windows 7 x64 as a second choice, it is able to run a lot more efficiently on older hardware than Vista does.
Both are great choices for Dolphin, both can run the x86, x64, x86 JITIL, and x64 JITIL builds of Dolphin just fine.