Hello to everyone on the forums I, most unfortunately, am a return customer. I finished the main story, and ended the Oblivion Crisis, which is the most I can say to not give any spoilers. I finished the Knights of the Nine quests and stopped Umaril and decided that my next objective would be to visit Sheogorath's realm of Oblivion in the Shivering Isles DLC. I remembered hearing about issues with the DLC and found out about the nasty ReferenceID bug that causes the game to quickly exhaust it's supply of RefIDs causing it to store any further additions [drops, etc.] to a temp storage which will be whiped once the game is closed. Playing after the bug takes hold can cause irreprable damage to your save.

I didn't want to lose all my progress for the sake of exploring the Shivering Isles so I found the official Bethesda patch download for the issue and once downloaded I attempted to run the patch. I ran it normally and as an administrator, both times it gave me an error message of "Old file not found." I searched this error and can report that I did not use the beta patch and I had the english version off of Bethesda's web site. It stated that the patch was for all of the english versions so I figured that there was no need to search for something region specific. I thought perhaps I should download the most recent patch available but wanted to leave that choice in the hands of those wiser then I.

I need advice, I wish to explore the final questline and the hours of extra gameplay that it promises, but I do not want to sacrifice my save and all my accomplishments in the process.

Is SI installed? If not then install it THEN install 1.2.

I have installed Shivering Isles, I even have the quest to enter Sheogorath's ream in my quest list. I have the Game Of The Year edition that I got around a year and a half ago, if it means anything. As stated in an earlier issue, it got packed away in a move. Is it possible that it was packaged with the patch already included?

Yes, the Game of the Year edition is already patched to 1.2.0416. You should be good to go right out of the box. If you're playing on a PC, you should seriously consider installing the http://oblivion.nexusmods.com/mods/5296, though.