|If you have a CD burner, you could make yourself a slipstreamed CD , preferably a CD-R for best drive compatibility, that has the contents of your Windows CD with the SP3 updates integrated into it. You use the same Product Key, and it's Microsoft approved. |
Nlite, as mentioned in response 1, is one of the programs you can use to make a slipstreamed CD - there are other ways of doing it too.
You need CD burning software that can make a bootable CD, such as a fully functional version of Nero Burning Rom, or there are freeware programs that can do that. Newer versions of Nero that came free with an optical drive have a Burning Rom version that cannot do that. E.g. I have Nero 6 SE that came with a Sony drive and it has a Burning Rom version that can, but only if you have a Sony drive.
NOTE that there is a bug in older versions of Nero Burning Rom you need to be made aware of, otherwise you'll end up with a non-bootable slipstreamed CD. Ask me about that if you need to.
If you don't do that, if you install Windows from your present CD, which probably doesn't even have SP1 updates included, you will have to load SP2 updates, and then SP3 updates - that will install most of what you need.
In both cases there will be additional Windows updates that need to be installed, but most of the ones you had before are now obselete.
All the original XP CDs with SP1 updates included I've seen have nothing printed on them to indicate that. However their volume label is different from the ones for XP without any SP updates at all, so you can use that on the web to determine which you have.
The original Windows XP CDs with SP2 or SP3 updates included have SP2 or SP3 printed on the CD.
You can't update XP with no SP updates to XP with SP3 updates in one step if you install Windows from the original CD - you have to load SP2 updates then SP3 updates - but when you make a slipstreamed CD you can integrate SP3 updates into XP with no SP updates no problem.