A machine of that era might have SATA II ports (if you're lucky -- it might just be SATA) which, as noted above, means modern SATA-III SSDs won't be able to achieve their full potential. However, that's mostly a theoretical limitation since most consumer loads don't stress throughput for any length of time; the real strength of an SSD is the low access latency, and you'll still get full benefit from that. You could save some money by shopping for an older SSD that only offers a SATA II interface; but I wouldn't go out of my way to try to do that, merely not worry about it if you find a good deal.
It's easy to clone your existing HD assuming the SSD is at least as large as the occupied space on your HD. If the machine has at least two SATA ports (if it only has two and there's an optical drive connected to the other one, you can "borrow" that port temporarily) you can just install the SSD on the free port, clone the drive using something like Macrium Reflect (there's a free trial version
that will work fine for this, or you can support Tech Report
and get a discount on the paid version), make sure you've got the drive letters assigned correctly, power down and physically swap the drive, and then power up and enjoy the speed. If you don't have a free SATA port (either vacant or liberated from your optical drive) you'll need to get something like an external USB drive housing (or find another desktop with two
free SATA ports)
Fortunately you've already upgraded to Win7, which mostly knows what to do when it sees an SSD (XP was a bit of a pain to use with SSDs, requiring a bunch of fiddling to get the offset optimal when formatting, etc). Once upon a time when SSDs were smaller, the OS was dumber, and we worried about the life-expectancy of SSDs, folks recommended a bunch of tweaks for SSDs. These days those aren't really necessary and people tend to over-tweak their SSDs (having a hiberfile and page file is fine unless you're really cramped for space; SuperFetch and Indexing can be left on; Win7 won't try to defrag an SSD but it will periodically "optimize" it by issuing TRIM commands, which is both safe and good)
The only other difficulty I see is that an SSD is 2.5" while your current HDD is 3.5". Therefore, an SSD will be too small to fit in the bracket meant for the harddrive. You will need to secure it by other means, possibly velcro or similar. Because SSDs don't have moving parts, it is less necessary to worry about how they are installed inside of a case.
Captain Ned wrote:
EDIT: As for mounting SSDs in remote corners of a box, a hot-glue gun will be your friend.
If, like me, you're not quite that ghetto, just get something like this
. As bthylafh notes, some SSDs include this in the box (they're usually marketed as "retail" or "upgrade" SKUs rather than OEM or "bare" drives).