LENOVO Y400 - Hard Drive Replacement Is a SSD compatable with this laptop? Is a SATA compatible?

Yes I have just bought two SSD drives for my old laptops and they work in them so you should have no problems what so ever with the drive, but remember one thing You'll have/need to install your windows operating system on them if you have the widows install disk If not then you'll have to buy one

I'm fine with all that and the other specs, but haven't bought a harddrive for a laptop in a while and just needed to know that portion.

HDDs and SSDs are interchangeable-the OS sees them both as storage. All that matters is that it is the correct size (usually 2.5" wide) and connection (generally SATA).