Ummm, I'm guessing you were using KSE to edit your quests so you wouldn't have to actually get the accelerator and get it to Gadon Thek. Unfortunately, the only advice I can give is to get the accelerator. I think the game checks if you have the actual item or not, instead of checking journal entries.
As for the disk problem, there's really not much to do except clean the disk or get a new one. Sorry.
P.S. Since this is your first post, I don't blame ya, but try to be alot more precise with your queries, problems, etc. in the future. It helps you and us at the same time.
Also, welcome to LucasForums!