So you updated to a SSD and enjoy the 10-15 sec bootup time but are getting annoyed by your system hanging now and then? Don't return your ssd yet, since it might be fixable with adding a little boot option. But be sure to especially read the part regarding SATA 1 incompatibility because in that case you might not have any other option than returning it and buy a different one.
When it actually happens
How to fix it (1. attempt)
How to fix it (2. attempt)
SATA 1 (SATA 1.5 Gbit/s) incompatibility
Most SSDs work perfectly with SATA revision 2.0 (SATA 3 Gbit/s) and SATA revision 3.0 (SATA 6 Gbit/s) and locking it to SATA 2.0 most of the times isn't really necessary. With SATA 1 (or correct: SATA revision 1.0 (SATA 1.5 Gbit/s)) it is a different story. If you already tried all of the above fixes and nothing worked for you, consult the technical specifications in the manual of your mainboard or computer and double check if your system might be equipped with only a SATA 1 compatible chipset. Because in this case there might be no other solution than a hardware upgrade to make this particular ssd work in your system. But there should be also some SSDs out there, maybe especially the non SATA 3 ones, that are capable of switching down to SATA 1. If you planning on upgrading a SATA 1 system with a SSD you should extensively search through forums and consult the manuals on the manufacturer's website. If you live in a country, where you can send a product back or return it in a shop even if you just don't like it, you should time your order in a way that leaves you enough time for testing and returning.
The very last explanation for your problems might also be a hardware defect. This defect must not necessarily be connected to the ssd but rather the controller on your mainboard that is responsible for accessing the ssd. Since a ssd demands much more from this chip, it is possible that an old defect now shows much more obvious than before. To be even more detailed: most of the times it is not even the chip itself, but rather the soldered connection that got cracks over the years. This actually happens if heat deforms the mainboard to a point, that the solder physicly breaks, what can only be seen under a microscope. Google "resoldering" or "reballing" and watch some videos to find out more about this possibility and how to fix it. BE CAREFUL since the chance is very high that you destroy your mainboard completely, but if you are planning to throw it out anyway it might be worth a shot. If it is still working kind of ok, you are trying it anyway and it breaks: we warned you!