Both Xp Service Pack 2 and Service Pack 3

well SP3 has MORE updates then SP2 and u need to have Sp2 instsalled to install sp3 install sp3 .. its worth it

Both are 'the best' if you think that way. Both pack are made up of all the bug fixes that are ready to download each day. You need to upgrade with SP2 before you can use SP3. Some people have had trouble with SP3 because it tries to upgrade to IE7 and now IE8 is available. Those upgrades can give problems on old PC's that are not powerful enough to run Vista. IE7 can then cause crashes. If you want the tabs feature of IE7 it is safer to load Firefox and use that for browsing the Net.

Service pack3 has to have some improvements over teh service pack 2. if it was not so, Why woudl Microsoft spend millions of dollars to make this service pack? The trouble is that when you use it i.e. hundreds of people use it some shortcomings do come up.Those shortcomings have to be projected and only then willthe problmes be sorted out.

XP SP3 is better because it has 3+ years of updates but it doesn't have new features.