You can clear it by editing the registry, remove HKEY_CURRENT_USER\Software\Adobe\Adept and all its subkeys.
Obviously normal backup the registry before making any changes applies,
and probably export just that part as well.
Try installing v1.7.2.. You'll still need to deregister and reregister, but maybe it will work.
You may even find that if you leave 2.0 around as well, after 1.7.2 has played you can get 2.0 to behave sensibly again (as sensibly as it ever does, anyway)
There are lots of bugs in ADE2.0 (and 2.0.1). Try replacing ADE2.0 with the older but more reliable v1.7.2.
(You can have them both installed at once if you like.)
Version 1.7.2, it is a little difficult to find, available on Adobe site for Windows and for Mac.
The forum software is sometimes corrupting the link above. There shouldn't be a blank in 'editio ns.html'. The following redirects to the same page: http://tinyurl.com/diged172
Some people have found ADE trying to upgrade automatically.
It appears (not 100% sure) that if you install ADE2.0 as a new install (not as an upgrade) that your 1.7.2 will continue to run.
Probably best to say no if 2.0.x installation asks if you want to migrate your library.