Concur, Crashs are either a hardware problem or more likely in your case a software problem. is NOT related to speed of Hard drive.
Let's see Old HDD is 250 Gigs with 150 free = 100 gigs used and you want to stick in a 64 gig SSD???
For a desktop (SSD + a HDD) the Mininium size is 64 gigs With a recommended size of 120/128 gig.
For a laptop with a single drive bay, the MININIUM is really a 120/128 gig drive.
Think this: a 64 gig drive is really only 60 gigs. Manuf count using fingers (base 10), computers use Base 2. Manuf like base 10 as they can advertise a Higher capacity, But they can't fool the computer. Just like HDDs when you format the drive you LOSE about 6%.
So Now you are down to 60 gigs, OOPS forgot MUST leave a Min of 10 ->15% free so that wear leveling, Gargage Collector and trim can work their magic, else the performance will drop considerably.
So 64 gig really is 60 - 6 = 54 gigs. That could be the same as trying to put 10 lbs of Shi* in a 5 lb bag.
To top that off, you need to be careful which SSD you get, Some SSDs can be fussy when placed in older sata II laptops, and to complicate that your running an older amd chipset. NOT KNOCKING your AMD laptop it does what you want to do with it, this is a NEGative directed @ SOME SSDs.