When I use PSI, I exit out of the program toolbar tab, then I also go into CCleaner > Tools > Start Up > disable PSI so it does not run on Start up. Perhaps this is why you were seeing it in the taskbar.
CCleaner is fine, as many of us use it here; use the Slim version so you don’t accidentally install the toolbar with adware unless you do a custom install and read what you are clicking upon installation. I run CCleaner everytime I go offline; I like to protect my privacy and keep a clean machine.
Instead of Registry Mechanic, I would recommend something like TFC by OldTimer, which you download to your desktop. It cleans deeper than CCleaner and you only have to use it occasionally (monthly at most) or after malware removal. http://www.geekstogo.com/forum/files/file/187-tfc-temp-file-cleaner-by-oldtimer/.
Run CCleaner first, then TFC second.
NOTE: When running TFC with OA, you need to be off-line and right click OA to “Close and Shut down OA” due to it’s self-protective mode. Then you can run TFC, which only takes a minute at most. Upon rebooting, OA automatically turns itself back on and all software are playing nicely again and your machine is sparkling clean.
TFC is completely compatible with Avast.
If you uninstall Registry Mechanic, the vendor’s uninstaller removal tool (Add/Remove Programs) often leaves remnants behind, so you may want to use (free) Revo_Uninstaller instead which gets the leftovers http://www.revouninstaller.com/revo_uninstaller_free_download.html.
If net framework is required for your system, it would have been installed and updated with your normal MS Updates. You should be able to find this under Add/Remove Programs.
I wouldn’t mess with adding PSI as trusted to IE right now or messing with the IE settings since I don’t know of others who have had to do this. I would wait for other input on this as well as contacting PSI about your problems and getting their input.
Just remember that when ever you install anything or uninstall anything, always reboot. Sometimes a program requires 2 reboots (it can’t hurt).