You are trying to reinstall Office 2003 or Windows XP? There are two service pack 3's one is for Office 2003 and the other for Windows XP. These are updates and you do not need new discs to get them. If you want, immediately install the standalone installers for the service packs after installing office or windows: XP Service Pack 3 & Office 2003 SP3. Regardless if you have XP Service Pack 3 installed you should be able to use your discs to reinstall your Office 2003. Note if you want to create an XP Service Pack 3 disc, use nlite. The first step is to copy your xp disc to a folder say on the desktop, then to use nlite to splipstream the standalone service pack (link above). You then create a bootable .iso fle and burn it to a cd. You use this cd instead of your original to install windows.   I guess you are trying to upgrade or install Windows from the desktop, in which case you would need to create the XP SP3 disc.  However you are best instead to copy all your files, documents, music, videos, pictures etc. to an external harddisc and do a clean install of Windows from the Dell BIOs. (Make sure you have your Windows XP Disc, your Office 2003 disc and your product keys for both of them). In this case ou can use your original Dell disc or a slipstreamed one. To do a clean install from BIOs, insert your disc into your machine, power down and power up while holding the F12 key, select boot from CD/DVD and follow the onscreen instructions, select format as NTFS where prompted. Then follow through with the install. Then install the standalone XP service pack 3 if you didn't slipstream it. Get the latest drivers from the Dell Website and install in the correct order. Then install Office 2003 and then the SP3 for Office 2003. Then you will need to select a browser and security and softwares. If interested I have what I use in a list below. Then copy your documents etc. back over. Note Office 2003 SP3 blocks out some old formats but there is a way to unblock it and the formats are quite rare. Your wordpad format should be fine. But I recommend back up all your data on an external harddisc and a clean install of windows (unplug the external harddisc while reinstalling windows) as I mentioned, this will give you the best performance.
Years ago bought Inspiron laptop Windows XP Home 2002 with Service Pack 2 and have reinstall disks for that.  Two years ago upgraded online to SP3 - don't have  any disks.  A month ago I unknowingly totally deleted Word and Excel trying to free up space.  SP 2 reinstall won't work on SP3.  My 'recovery' date is only 24 hours ago. How can I get Word and Excel back on SP3?  If SP 3 is reinstalled remotely, will it wipe out my docs that are saved in wordpad form?  Would appreciate any advice!  
Recover/reinstall Word & Excel on SP3 without disks (installed online)