I had AE2.1 installed under XP and then went thru a series of upgrades 8->10 but AE 2.1 wouldn't start, however it was installed... I tried the above 2.6 upgrade and it wouldn't run even with the original CD in the drive.
So, I'm in the same boat... then I discovered I could install it on a laptop with Win 7 on it- the install indicated it was not compatible but gave me the option to install anyway.
After it was installed I could run AE2.1 and download videos to the HDD and then use the network to get them over to my W10 box... I hope now I can use something else to edit them.