It won't help when you uninstall FH2.
Today might be a EA Server Service Day, try it again later this evening. Shouldn't that help, then you have to check your Account files under .../my_documents/BF2/Profiles/... it seems something messed up your Password or Account name, so you can't register to the Account Server. Always make a backup of the profile files should you use a fake email addy and odd passwords. It helps.
Edit: To answer your question, which has been answered before in this section: To uninstall FH2 you just have to delete the FH2 folder under .../Battlefield2/mods/, the fh2.exe in .../Battlefield2/ and the shader cache in by deleting the folder fh2 under.../my_documents/BF2/mods/