Your XP2.1+ is a Palomino core and is one of the hottest CPU's AMD made, from what I can remember this CPU produces around 79watts of heat, to put this into context the very latest XP2.8/3.0/3.2
generate a similar amount of heat , just as a side note, the original Athlon 1.4 was also a bunsen burner of a CPU with a similar heat output to the XP2.1+.and XP3.0+
Basically all of these CPU's are the last in there respective core ranges so have pushed that particular core to it's thermal limit.
Last Thunderbird core: Athlon 1.4
" Palomino " : XP2.1+
Possibly the last Barton? : XP3.2+
All reaching there design limit and producing very large amounts of heat.
So to put this in practical terms, owners of an old Athlon 1.4 require the same sort of cooling as those with XP3.2+'s and your XP2.1+ falls into that super hot bracket.
Get yourself a copper based or all copper cooer with a high CFM fan rated at 2.7 or above.
Martin
Replying helps further our knowledge, without comment leaves us wondering.