I've got a collection of HS21s (type 8853) that need a memory upgrade. Crucial's recommended memory kit is http://www.crucial.com/uk/store/mpartspecs.aspx?mtbpoid=6C00BFBAA5CA7304.
Searching around a bit I've found some "DDR2-667 PC2 5300P ECC Registered" memory for a considerable amount less. Seemingly the only difference is that it's 'registered' vs 'fully buffered'. Is this going to be compatible, and if so, what am I compromising on?