It's great to hear that you've decided to play Plant Tycoon again! We have always been very fond of Plant Tycoon (we first created it 20 years ago for the Palm Pilot)!
Unfortunately, the virtual seed tray, as created by Borg (one of our forum community members), will not work on today's Windows versions due to the vastly tighter security of modern operating systems. Even though the game data is visible to you, it is not accessible to the virtual seed tray.