About This File
First of all: This isn't my file!
It's a release of a file that used to be hosted at the UESP. Now many links to that page fell under a nasty attack a few years ago, so much of the useful info related to the usage of Oldblivion has gone forever. For further info see this post to AKB at UESP (the last link may die soon viz. the UESP archiving system but it will be in the archives)
For anybody wishing to sample Oblivion on a very old machine, with an old card (think 256mb or less), or in VirtualBox or VMWare (think 2000, XP or Windows 7 at most) and the DX drivers are compatible with newer cards(big ask) then try this!
Most info on getting started is in the included readme.txt file.