<<Anyone know specifically about oem and retail IBM hard drives?>>
You'll have to deal with the OEM that the drive is sold to, IBM will not support ANY OEM hard drives. There is a difference between "OEM" and "bare", both come in w/o any kind of packaging, neither will have bundle software, cables, screws mounting brackets and such. But the difference is that bare drives meant to be sold to end users or computer shops and they do carry the same warranty as retail package. OEM drives are sold to vendors like Dell, Gateway and Micron alike, to lower costs, OEMs agree to run the warranties themselves, saving IBM a lot of trouble, therefore you'll have to get warranty through the OEM. But in many situations these OEMs will not honor the warranty unless if the drive come in their PC.
Other manufacturers such as Seagate and Quantum will look at the situation and decide whether to warranty the OEM drives. Maxtor's "no quibble" policy will warranty all drives, regardless of whether they're OEM, bare, or retail. However, all of these hdd companies will recommend you to try the OEMs first.