If you've tried to open a Peachtree company file on a computer that serves company-files but isn't actually running the Pervasive engine, Peachtree can irrecoverably hang at startup.
Using the Registry editor, find and modify:
HKEY_CURRENT_USERSoftwarePeachtreePeachtree Complete Accounting14Options lastcompanyopenlong
and set it to the "real" company file -- or to a legal filename that doesn't exist. Then Peachtree will start and you can re-point it to the correct location.