You said "H200 or 6/iR" ... you might be better off with the SAS 6/iR, as that controller is also used on workstations that do support XP.  You can find the XP driver on the download page for the Precision T7500.  The H200, your ONLY chance is that the 2003 driver will work (as they do sometimes but not always).
Hi, Followed by this post, does R210 server supports Windows XP Pro SP2 32 bit with raid?Requirements are: Raid 1 on 2x500GB sata with perc H200 or 6iR.  K. 
Does PE R210 Supports Windows XP with Raid?