I've installed Armory wallet management on my PC (Windows 10) and it's just running through the "Build Databases" phase with Computing balance box showing one second....
It's been like this for over 24 hours and it's still showing as node offline.
Unfortunately, it sounds like something has "broken" somewhere...
When I installed bitcoin core it was a very large download and took a long time to synchronise databases.
Is this the same ??
Sort of, but unless you have a VERY slow PC, I wouldn't expect it to take more than a few hours... my old i5-3570k with 8 Gigs of RAM can redo the Armory databases in about 2 hours.
I'm wondering if I maybe have a corrupt download of armory or does it just take this amount of time to build databases ??
I don't think it's a corrupt download of Armory, but possibly either some corrupt blocks in Bitcoin Core... or you're running Bitcoin Core in "pruned" mode... or Bitcoin Core is not configured to properly accept connections from Armory... or Armory is not configured to connect to Bitcoin Core properly.
Can you please post your log files? Either use the "Export log files..." option in Armory, or find the armorylog.txt and dbLog.txt files in your Armory datadir. They're quite likely very large, but if you use:
https://pastebin.com/ you'll be able to copy/paste the contents of the log file there... then click "create new paste", then you can copy/paste the uniquely generated URL of your paste here.