HDD rotational speed

Here is another one: http://en.community.dell.com/cfs-file.ashx/__key/communityserver-discussions-components-files/3518/4062.aida64_5F00_D430_5F00_.TIF

Does it mean that I can ask for a change or replacement?

These are basically hard drives designed for MP3 players like older iPods - they're not performance drives.  Chances are it has adaptable spindle speeds -- in fact many drives now do (especially the "green" drives).

Here is the image:http://en.community.dell.com/cfs-file.ashx/__key/communityserver-discussions-components-files/3518/4380.hard-disk-sentinel_5F00_D430_5F00_a.TIF

If you mean you bought the drive on the premise of it being a 5400 rpm unit, ask the seller.  If you mean it came with the system - no way;  this is a 4-5+ year old computer.

There aren't many of these drives left on the market - Toshiba and Samsung are the sole manufacturers (and since Seagate is taking over Samsung's drive business, those may disappear as well).

There's just little market for these - the market will totally disappear the day Apple stops making hard-drive based iPods.

I bought this directly from Dell via website at 2008 year end. The invoice stated it is a 5600rpm HDD. I had send an email but no reply from them, almost a week. My 3 years warranty ending soon.