You were given bad advice.
Return/Sell the SSD and buy a 7,200 RPM hard drive instead, it should work fine and a more of a match for your older machine.
Your Mac doesn't have the faster SATA connections for a SSD also 10.6 isn't equipped for SSD's only hard drives, your basically putting a Ferrari engine in a Yugo, it can't handle it.
The 7,200 RPM drive will give you the performance and more drive space than a SSD anyway.
Follow these instructions when you erase and install 10.6, it will give the best results.