Hello. The attachment feature is an improvement in image handling. Access 2003 was incredibly braindead in imbedding images. If an image file in compressed format, such as JPEG, was imbedded the database size would increase by the size of a corresponding uncompressed bitmap (!!). More remarkable is that this behavior was the same if you asked it to link to the file. In contrast, MS-Word handles linked images the way you might expect (file size increases neglibly). The only tolerable way to put lots of images in a Access 2003 database was to use a hyperlink (ick) and/or a low-res thumbnail (ick).
Access 2007 attachments are a curious beast. It pretends to keep a reference to the original file, reporting a list of the file names. However, the file is actually imbedded in the database file. You'll see that if you move or delete the original image, that the attachment is still there. If you try to open it, via the attachment manager, Access will automagically create a copy of the file in a temporary internet files directory for the default viewer to open. The main improvement over Access-2003-style imbedding is that the space it takes up in the database is *only* the original size of the file (not an uncompressed bitmap). In my opinion they should have just fixed the broken functionality in 2003 (but then MS couldn't tout it as a new feature!). Anyway, it does make life slightly more managable if you want high-res images in a database. It also does quite well for attaching highly-compressible, line-art type images using PNG format.
Cheers!
Richard