Hey, I'm have an old Dell laptop from 2005, which is starting to feel pretty slow. And thought that putting a SSD in it could expand its lifetime a little. But is their anything which I should think of before trying? And would it actually help me? Since I'm kinda interested in this experiment in general I'm not gonna give you the specs of my laptop just say that it supports SATA150 and currently has an 4200rpm HDD.
SATA150 shouldn't be a very big issue because the big benefit of an SSD is it's very fast access time, not it's transfer rate. You'll still get almost all of the performance improvement for tasks like booting and starting applications even if the transfer rate is cut down a bit.