Moving this discussion to the Adobe Digital Editions forum.
Which operating system are you using? Do you receive any error messages when you try to install? You may want to also review Installing Adobe Digital Editions 2.0 in Windows Vista - http://helpx.adobe.com/digital-editions/kb/installing-digital-editions -20-windows.html.
If Geoff's suggestion for Vista does not help, post more details about your system and the exact problems.
Also, you might try installing the older version which seems more reliable.
Version 1.7.2, it is a little difficult to find, available on Adobe site for Windows and for Mac.
Thanks, I have XP, but tried the one they suggested for windows. Will try again.
I'm not sure whether Goeff's suggestions for Vista also work for XP.
He was going to try it out when he got the chance, but I'm not sure if he has managed it yet.
If you search around the forunm you will see that quite a few other people have had issues with V2.0 and XP.
Good luck with trying again; but if not do try the earlier one as above.