As I've mentioned in a previous discussion:
If any PTC Community member wishes to disable their account all they need to do is email us at: community@ptc.com
Please keep in mind that you will need to use the email address currently associated with your PTC Community account so that we can verify your request.
We do not delete database records for fear of lost data. It would be a shame if a member asked us to delete their account, only to come back years later asking for us to recover their account (it's happened). Luckily when we disable an account all the user has to do is email us again requesting the account be activated once more.