Garrett- welcome,
What version are you using? If it is the Deluxe (32 bit) or Ultra (64 bit) then there won't be a lot of "extra" stuff such as content packs and premium extras installed with PD 11.
Version comparison:
http://www.cyberlink.com/products/powerdirector-ultimate/compare_en_CA.html
Since you have PD 12 installed and working successfully (there is a new PD 12 update / patch build 2109. Make sure to install that if you haven't already done so:
http://www.cyberlink.com/support/powerdirector-ultra/patches_en_CA.html,) then I think you can safely go ahead and uninstall PD 11.
Oh and when you say "delete" you do mean un-install first and then delete the left over remnants?
If you upgraded from PD 11 to PD 12 I would suggest you hang onto the older PD 11 install files as a backup and save your activation keys for both versions just in case.
Rob
PD 14 Ultimate Suite / Win10 Pro x64
1. Gigabyte Brix PRO / i7-4770R Intel Iris Pro 5200 / 16 GB / 1 TB SSD
2. Lenovo X230T / 8GB / Intel HD4000 + ViDock 4 Plus & ASUS Nvidia 660 Ti / Link: https://www.youtube.com/watch?v=ZIZw3GPwKMo&feature=youtu.be