Can someone help me with my PSP problem?

[rbbmayyambbr99]

A little history before the problem/question:I stupidly let my friend put homebrew on my Sony PSP, and so today I decided to get rid of it, because of the newest Sony Update (3.51). The homebrew started at 3.10 OE-A, and I downgraded to official firmware 1.5. Now when I try to upgrade to 2.00 from my UMD, It won't work. Then, I tried to upgrade to 3.51 by downloading that update from the Sony website. That doesn't work. Every time I attempt to update to 3.51, it tells me the system is incorrect, and the update could not be completed, or something to that effect. the error code is: (DNFFFFFFCD). I looked this up, and I think it has to do with Sony's downgrade check in 3.3 firmware or later, but this doesn't explain why the 2.00 on my UMD won't work.So, to the question. Can someone here help me get my Sony PSP working? As in updated, and basically totally stock/official?Please, help.