PCSX2 needs overclocking.
No$GBA needs overclocking (yeah, I know you can get away with not overclocking this, but... it's not going to be as smooth as on a real DS. How can I tell? I have a real DS)
Supreme Commander needs overclocking.
CRYSIS definitely needs overclocking.
Photoshop also needs an overclocked system to run fine.
3Ds Max also needs an overclocked system to run fine.
Is Vista THAT bad? Yes, when you run too many things at the same time.
So it's just a choice, but it's better to overclock in general.
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cChip interpreter WIP - current status: Release Candidate
LRx Filter RC - current performance rating: 9/10