http://esupport.sony.com/US/perl/model-documents.pl?mdl=VGNCR220E shows 5 varieties but the size limit can be a factor of what OS? For example I keep Windows XP and Windows 2000 to 120GB drives. XP SP2 removes that limit.

Using the details at this link show the usual SATA drive. Today you should be able to fit the usual 1TB drive into that and be able to limit the SATA speed if necessary.
Bob