Playlists Missing After Install New Hard Drive and Upgrade to Win 7

Question

My computer needed a new hard drive and I upgraded from Win Vista Home Premium to Windows 7 Home Premium.
I am trying to get my Playlists back for my iTunes in my "Administrator" user account, after reinstalling iTunes and putting my music libraries back onto my computer.
(I had installed 32-bit Win7 OS myself, computer worked OK for about 1 day, then would not boot up; I took computer to shop, they said I needed new Hard Drive, and I gave them my new Win7 OS computer disks)
I am confused over whether I have 32-bit OS or 64-bit OS. They recommended installing 32-bit OS, I agreed, and believed that I had 32-bit OS installed; however, Computer / System Properties state "System type: 64-bit Operating System"
Prior to my installing Win7, I backed up the following onto my Western Digital "My Passport Essential Portable Hard Drive:"
("My Administrative Account"): Users / Owner / My Music
and
("My User Account"): Users / Yank / My Music
My "Administrative" and "User" user accounts contain different songs in iTunes.
If helpful, I could describe what is in each of these 2 backed-up music folders.
To get started, I copied both my "Owner" and "Yank" user folders in the C: User folder; however now I have "Owner," "Yank," and "Yank.Owner-Toshiba" folders in the C: User folder. I think I did this by creating a new Yank user account by creating a new account, not by my copying a folder into C: User folder. The Owner folder has a picture of a lock on the folder icon.
Because I had trouble merging My Music folders in the Owner folder, and I was confused, I copied everything that was in the Owner folder into a new folder in the Owner folder, "NEW OWNER FOLDER." I also copied my Owner Music folder into several places in my Users / Owner folder.
I also ended up changing the "iTunes Media folder location" several times, using iTunes "Edit / Preferences / Advanced tab / change "iTunes Media folder location". When I chose "Reset," it shows "C:\Users\Owner\NEW OWNER FOLDER\Music\iTunes\iTunes Media"
I've also played around with "Edit / Preferences / Advanced tab / 'Keep iTunes Media folder organized' "
When I open my iTunes, I have no playlists.
However, when I went to my "Yank" user account and opened iTunes for the first time, the playlists associated with that account were visible.
How do I get my playlists back on my Administrative Account, which is my main song collection and had many, many playlists?
Thank you.

Answer 1

YAY!
I didn't try shift-start of iTunes, but I DID GET MY PLAYLISTS BACK BY FOLLOWING YOUR OTHER ADVICE:
I went to my external hard drive, went to my backup at Users / Owner / My Music / iTunes / and searched for library.itl
Four files with that name were found, with different dates.
I chose the most recent, dated just a few days before I made my backup to the external hard drive.
I copied it to my computer's hard drive into the following location:
C:\Users\Owner\NEW OWNER FOLDER\Music\iTunes
which overwrote the file which was located there.
When I opened iTunes, ALL MY WONDERFUL PLAYLISTS WERE THERE!
THANK YOU SO MUCH FOR SOLVING THIS FOR ME!
CAN YOU IMAGINE HOW DISAPPOINTED I FELT WHEN I BELIEVED THAT I HAD LOST ALL OF THE PLAYLISTS WHICH I HAD CREATED OVER THE YEARS? Many of my playlists were composed of whole albums whose songs I had added to iTunes.
THANK YOU AGAIN SO MUCH!