Program----------LinearX FilterCAD 16 bit analog filter design software with authorization key.
History-----------Has worked fine on 5 machines running Win 95 @ 98 over past 8 years
Problem----------Recently installed XP PRO and get error "KEY NOT FOUND"
So far I've tried--1 un-install and re-install.
2 Enabled win 98 compatibility in properties.
3 Verified it still works on my laptop running Win 98.
4 Verified that all my other installed 16 programs are functional
Question---------Doe's XP PRO interface differently than Win 98 with the parallel port where
the DONGLE (KEY) attaches? Any other ideas as to what might be the
problem, please advise.

Have you contacted the software provider and found if the program is supported on XP. This could be a issue with the software interface on XP. Dongle Keys should work the same but there are alot of interface changes between Win98 and XP. There maybe a upgrade to the software availiable for XP.

I contacted LinearX service and the only solution the tech. could offer me was to upgrade to their latest software at a cost of over $1000.00. I paid over $3000.00 for this program 8 years ago and feel they should support it with macros or something which will allow me to upgrade my OS as needed. It goes without saying that I will never do business with this outfit again. Are you aware of any other programs that are not foreward compatible with MS OS upgrades???

Programs that are known to experience a loss of functionality when they run on a Windows XP Service Pack 2-based computer, click here.
Your specific program is not on the list. Although that is not much help.
I highly doubt this is a complete list. But at least you know it does, and has happened.

Found an item listed in the FCAD file folder titled VERSION.TXT Opened it and found a list of all upgrades and their dates. The most recent version 1.14 states "Added support for WinNT operation and new installer. November 27, 1996." I purchased this software in 1998 as version 1.14 so it must be NT compatible.