Thanks but the issue got resolved late last night. After my old hard drive crashed, I had some pics on it that I wanted to save. I installed the old hard drive as a slave drive and copied my pics folder and then also copied my Oblivion folder. I could play the game that way but I couldn't download the patch. I thought I could just reinstall Oblivion over the old copy. I tried two different Oblivion discs and got the same error. So I just deleted all traces of Oblivion from my computer and it reinstalled perfectly. I patched it last night too and added my expansion pack. I feel like an idiot now, but at any rate, tragedy diverted, I can now play Oblivion.
Thanks for your attention.