The issue is that OSes prior to Win 7 did not provide the TRIM command which is needed to provide garbage collection and other functions needed to keep an ssd humming well. An ssd will certainly work fine with Vista at first but performance will gradually diminish due to the lack of TRIM.
There may be manufacturers that provide a TRIM utility for their ssds that can be run manually on OSes that don't have the support built-in. I believe Corsair and Samsung provide software for their ssds that provide TRIM for older OSes.
Garbage collection is done from the controller, but TRIM comes from the OS. If the OP has a decent branded SSD with good software he can do TRIM from the software. Corsair and I believe Samsung can also allow a scheduled TRIM command be sent.