Can't access older Time Capsule back-ups

I should mention that when I do ask it to show me back-ups, only two windows form, and beyond that there is just the grey placeholders for other windows. When I tried looking up the data I'm searching for from an older computer I had wiped clean, it has the outline of many white back-up windows... but unfortunately, somehow erasing my computer somehow must have erased everything from that computer on the Airport Capsule as it showed no back-ups ever done.

Oh, sorry for the confusing - I had erased my old computer, not the one I was discussing in my original post.

I had decided to see if I could salvage the file I wanted from the old computer - I had Migrated that file (and many others) to the new computer that I got two years ago. It is (so far) the only file corrupted by the Migration (or something else?) so I have been trying to use Time Capsule to see the original file. But I can't get into the old backups for Time Capsule on my new (2 year old) computer. That's what this thread is about.