How to make xp pro sp3 iso from sp2 disc?

hi guys
I haven't had to fool with xp in awhile and need your guidance.
I have a good HP OEM XP Pro SP2 disc, and need to fresh install xp pro on a dc7600. good license/coa etc all in place. to save time I want to build an iso that installs sp3. i use imgburn to extract the cd but how exactly to I build that new sp3 iso all-in-one??
when its done I plan to stick it on a flash drive and ... bam.

appreciate your expertise

 

I have never been able to slipstream an OEM disk, at least not a Dell. I doubt it will work better with a HP.