It may only be an Ebuyer problem but I intend to buy a Seagate 300GB or 320GB SATA drive from Scan which is specified as having a 5 year manufacturers warranty. As these are presumably OEM units are SCAN confident that Seagate will accept the 5 year warranty period. The Seagate warranty states that the 5 year warranty is only for distribution units (whatever that might mean).
On a side issue - other than the fact that the 320GB drives has 4 heads and the 300GB model 3 heads - is there any practical difference between the two to justify the price difference