|"I used an xp media center reinstallation disk.."|
A DVD ? It won't fit on one CD.
If it was two CDs, you have to be careful that you insert the second disk at the right time, and insert first disk again at the right time, otherwise Windows MCE is not installed properly (there are bugs in MCE's Setup - the disks it asks you to insert have the wrong label [description] , both times that it asks).
Unfortunately running a Repair installation of Windows can't fix every problem. Once you have copied what you want to save to elsewhere, you're going to have to install MCE from scratch, then go the Dell web site and get the software downloads required for your system and load them, or, if the model came with a Drivers and Applications CD, you could load those instead.
If the network adapter drivers are not loaded when Setup is finished, you will have no access to the internet. Either you have to get at least the network adapter drivers on another computer, then load them on your computer, or if you have the Drivers and Applications CD you can load them from that.
If the Windows installation does not have SP3 updates included, the best time to install the SP3 updates is right after you have installed Windows from scratch, BEFORE you have installed anti-malware software.
See Response 6
"If your XP CD does not have SP3 updates included, the best time to load them is right after you have installed Windows from scratch...."