Thanks for the reply and solution MrSykes.
I uninstalled adobe AIR and ran a file and registry cleaner to delete any left over files and installs.
Then installed the v.15 Adobe AIR beta as recommended.
The cleaners I used (ccleaner & jv16 power tools) did find some temporary install files and remnants of the Video Alchemy install.
Tried the install again and still no installation window displays.
I'm running Windows 7 on my PC and even changed the installation file compatibility to Windows XP service pack 2 to no avail.
Funny that it installed fine on my notebook with Adobe AIR latest version running Windows 7.
I'm watching task manager as I'm attempting the install and videoalchemy.exe has some cpu usage then drops to zero activity.
Then Adobe AIR application Installer starts up then cycles to zero cpu activity.
I'm stumped on this one :-(
Thanks again for investing the time on my behalf.
Regards
Stephen