After searching for years on how to do this I finally came across a hidden setting that lets you modify or delete parameters set by PDM. I'm sure this is discouraged by big PTC for a million reasons but like most anything dictated, there are valid reasons users need this level of function. In my case, my start parts have been polluted for a good decade since I unknowingly at the time, laundered them thru a client site where they used PDM. The below was performed and tested by me on my system, and should work on any install so long as you are not attached to any PDM system. If you do have PDM at your site, you can try this by running a solo session at your own risk, or by killing the registration to your PDM mothership thereby leaving you with a stand alone session. Personally I'm a one man army so my vault is hand woven and governed by a friendly librarian already so, I freely allow such changes LOL. Also, this should work on many a version but I can only attest to this when running pro 34 because I'm on the latest downgrade here. If you have an old version and this doesn't work, please report your findings.
Anyhow, here is how you too can unburden your parts, templates and assemblies from unwanted locked parameters. From inside pro/wildfire/creo go find your config.pro which in Creo 3.0 language is hidden at:
File > Options > Configuration Editor
That pop up will show your config. At the bottom of that pop up, below your config options, there are three buttons, Add, Find and Delete. Pick the Add button and enter this:
For option name: allow_create_pdm_param
For option value: yes
Say ok and if warned about your session and all that, say yes and let it save to your config.pro for later, whatever you wish. Once you have this gem set, open your parameters and check the difference. In either part or assembly mode, now hidden in the Tools ribbon tab on Creo 3.0 is a pick for Parameters. Click over to that and once open enjoy your new found freedom. By the way, the ribbon can be scrolled with the mouse wheel sometimes, just hover the area and spin back and forth to flip thru tabs. Since you're likely in the Model ribbon, slide the mouse up high and in the general ribbon area, roll the wheel back a few clicks and see if that hidden function suits you as well. Here, I added it to the quick access toolbar so its now clearly indicated by the square bracket hieroglyphics so I don't have to play hide and seek for it anymore.
FYI - If you are hardcore and want to find this option on your own, you'll notice that your effort to find this option only proves it's not there. Well it is there, not only that but it works. However, like many things Creo, and like the modify menu, and like several surprise pop up instances of the menu manager, you can't have it unless you know the secret password or trip over it as an Easter egg. Anyways go ahead and try the search for the term 'allow' and see what comes back. Couple things there but notice the value I posted isn't one of them. So without derailing my own thread, just enter the option as typed above, save it and enjoy. No exit needed, do not reboot, results are live and working once clicked... yeah, what software am I running again???
Oh, so if you are not in a session of pro when trying this, I bet you can get this in using notepad to edit your config, otherwise just be in pro and enter it on the fly as shown. Once this option is set and enabled, you'll notice all that greyed out stuff is gone and you are free to change or delete any parameter as long as that parameter isn't in some relation somewhere. If you find something that still won't delete, check your relations. If the value appears in a formula somewhere, pro won't delete it. I had two relations myself and once I killed them, I was able to whack their parameters as well.
Hope this helps someone else, it sure helped me.