I have an Alienware M17x and have been thinking about putting a SSD into it. I have a 500GB hard drive in it at the moment and I know that I can up at second hard drive into it. But will I encounter any problems if I put a SSD into it. Also any suggestions of what SSD I should get would be appreciated.
How much used space do you have on your 500GB? What I would do is pick up a SSD that has enough capacity for your OS and the used space and use your current drive as a data or app drive after you transfer the data to the SSD. Then I'd boot to the SSD to see if it works OK. Then I'd format the old mechanical drive and use it for new apps and data.
There are Apricorn data transfer kits that can help you swap out your HDD with your SSD. Some drives come with these kits.
Samsung 840s are really affordable now in higher capacities. I like Intel drives, too. I would suggest using the model with a capacity larger than your current drive's contents. Some will come bundled with data transfer kits as well. You could also save money by looking for SATA II specific drives as I believe the motherboard on that laptop supports SATA II specs and not the latest SATA III.