Can RAW images from Aperture library stored in an External HD?

Question

I last night[I thought I did] stored projects from aperture library to an external Iomega Mac version HD.[Partitioned the Iomega into two One large225GB for Time Machine and small 125GB for just back up folders]
Then I have reinstalled my Mac OS.
Now I connect the HD to my Apple Mac Book Air and see the saved images on the external HD but not highlighted and not there for available to open in my Aperture Apps?
I also tried to import selectively the Aperture images from my Time Machine back up and that too failed.
I on opening the Aperture selected "Import photos form a Disk" but that failed too.
I have also saved to the same external HD some modified photos saves as JEPG and they open ok.
When I reinstalled the OS and registered in a different name, would that make any difference to importing Aperture projects saved on an external HD?
Can anybody suggest a way to open those Aperture project folders that I have stored on my External HD?
Regards

Answer 1

Projects are entirely maintained in the Aperture Library. You can use 'referenced masters', in which your masters don't reside inside the library (and the library merely keeps track of where you decided to keep them.)
When you import new photos, Aperture updates some information in the library so that it knows the photos exist, where they reside, what sort of changes you've made to them, etc. You can't just plop new images into an external folder and expect Aperture to notice them. Think of this as "formally introducing your photos to Aperture" -- via the import process. Aperture wont deal with any photo you haven't introduced to it.
I would be remiss if I didn't mention the alarm bells and red flashing lights that went off as soon as I read you were keeping your photos on an external drive partitioned for Time Machine and backup folders. Bad bad bad.
There are two types of disks in the world: (1) Those that have failed, and (2) those that are going to fail. Sadly, even backup drives are not an exception to this rule.
Never keep the "working" copy of your data on the same physical drive as a "backup" copy of your data. When the drive fails (and someday it will) you'll just lose all your copies of your work -- so much for having a backup. Drives are very cheap these days. Just get another one and dedicate your backup disks just for backups.
As you have a MacBook Air (and thus only a single USB 2.0 port) you might want to look into "Network Attached Storage" (aka NAS). This way you don't have a tangled mess of a USB hub hanging off your Mac with several disk drives also hanging off the side of your Mac. The disks just live on the network - as though they're remote file servers. If the network is connected via Gigabit ethernet, the effective throughput to read/write those drives is about 3x faster than a locally attached USB 2.0 drive (no kidding!). You might think this is really expensive -- but you'd be surprised. I was checking prices at Other World Computing recently (an online store of products targeted to Mac owners) and noticed you can buy an empty NAS enclosure (meaning you buy the disk to go inside it) for as cheap as $25! An enclosure with 250GB disk pre-installed and Time-Machine compatible was about $120. To put this in perspective... I recently paid about $150 for a B+W Circular Polarizing filter. So all this technology costs less than one decent lens filter for my camera.