I had an old account (two very popular reviews) which I would love to associate with my current one (100s of reviews). Unfortunately, the old email address involved with the old account no longer exists. Any chance I might be able reclaim the old one or merge it with my current account?
IMDb cannot merge accounts. If the server that provided the old e-mail still exists and you remember that address then you could get a new (old) address again and re-use it. If you can remember the old account address and its password the e-mail provider is not necessary, unless you need a password recovery, then you would need the address.
A 2nd best idea if you want to link to your old profile would be to go to your user profile and edit it to add something like 'Old Account & Reviews [link=whatever your old user link is]' then any interested parties in your reviews have a clickable link to your older reviews from your profile.