Firstly, definitely go with the SSD, you will not regret it, and will be pinching yourself if you got the HDD and you knew how good the SSD was. But yes, I'm geussing you have a laptop, if so then the SSD will most likely be compatible, as well as the 2.5" HDD. However you will also need to either use a DMS (Data Migration Software) to transfer all of your files from your old Hard drive to you new storage device, or an alternative which I probably wouldn't go for but is a shout, get an external HDD for Mass Storage then just get a 120GB 840 Evo, make that your boot drive and put your most used programs e.t.c on it. It's your choice, but (I'm going to assume you want to do this) if you want ALL of the files you have on the SSD, ALL of the storage, and just switch it over to your new SSD, then the DMS is the way to go. You might have to check your space on your Hard Drive currently, because you might find that 250GB will not be enough, then you will be in trouble.