Hi,
Yes, they can work on older machines.
But to get the best out of SSD drives you really need SATA-III
Check how your current drive(s) are connected.
SATA connectors look like this.
"Pictures"You may get an idea in:
Menu > System > System Information and look in PCI Devices
or
If you have no docs for your PC/Laptop
Go into BIOS,
It may show drive & settings details in there
Info:
Most SSD's come in 2.5" format, so may need adapter if you have 3.5" slots
You can also get SSD's in mSATA format, for new PC with slot's on Motherboard
There are even new high spec m2 format, for mini sockets on motherboards.
and interesting things like these to put
RAID in a 2.5" format with 2 X mSATA cards