Butter fingers,
I fwel deeply for you as I have had similar problems once before.
I know its frustrating. As long as you have backups of everything I would not feat that you will lose everything and wont be able to proceed. Theres an answer somewhere.
Not sure I can point anything helpful out :
When you are going through prcedures of installation/removal make sure that you do it following a reboot and you may have to exit FPSC an reboot often whrn trying to solve probs like this.
FPSC keeps its temp files in MyDocuments Temp Directory. When attempting such things as reinstalling/removal when you have probs - after removal always empty the temp folder before rebooting - FPSC always leaves one file it wont let you delete - presumably the last in use held in memeory - (sometimes if you try to remove/re-install while this is in memory FPSC can refuse your action} - on reboot check the FPSC temp folder again and see if you can delete any files still there - If not dont worry about it.
Only then should you try a reinstallation after rebooting if you are having problems.
Before attempting all this you may also have to delete any other and all instances of FPSC and it files i.e. clean your system of any references it may make to any file dependancies anywhere on the system.
All of this is rather servere action so I would try everything else first.
I have said this before : when I had a similar problem I went through all of this and got it fixed - god knows how - just by deleting everything relating to FPSC I could find numerous times - removing/reinstalling and so on many times until I got past anything stopping the correct installation and functioning of FPSC
Later again it happened once more when I recieved the same error message as you have specified and I discovered that it had been caused by exceeding the script or map object limit so no matter what I did until you reduce to below the limit FPSC wont run.
In the bug reports Board theres a thread which I posted regarding the error message 108 - 10181 - caused by exceeding the script limit - resulting in similar difficulties of not being able remove/install FPSC correctly. It game me serious headaches too. In fact there was no need to do so I discovered and had wasted much time as the answer was simply to reduce the number of scripts.
On speaking to Lee at that time he comnfirmed there was indeed such a limit which had been unknown to users previously.
Heres the link to the thread.
http://forum.thegamecreators.com/?m=forum_view&t=67052&b=28
Its a large thread and if you are going to read it you might as well read it all or browse to somewhere near the bottom where the results of solving the issue and findings are at least in my case.
You can see what happened to me is almost exactly as it is with yourself.
Cant say it would help you but it might.
Good luck. Dont give up you'll crack it in the end I am sure.
If all else fails I would try just removing FPSC or deleting the folder and copying back a complete "Copy" of the FPSC folder and all of its contents - a previous installation when it was working correctly - that should solve your problem as it should put you back to a fully working version.
Users do backup I hope and that should include occassional complete backups of yor FPSC folder in its entirity - when something serious goes wrong - thats when you realise the value of them.
"I am and forever will be your friend"