Well, I own WB through Object Desktop, and I see the "purchase reminder" screen too.
I used to have WB 4.60.048 installed and everything was fine: no nags, no crashes.
I then used Stardock Central to uninstall 4.60, rebooted, and installed WB 5.01.006.
I found that 5.01 crashed (in the wbconfig screen) as soon as I clicked on one of several skins that WB4 had no problems with (such as Antares or Apogee), so I wanted to downgrade.
I used SDC to uninstall 5.01, rebooted, and used SDC to install 4.60.048 again.
NOW, everytime WB starts up, I get the purchase reminder nag screen. I looked in "About Windowblinds" and it does not mention being the shareware version.
I'd appreciate it if someone could help me make this inappropriate screen go away.