You can restore  your site..

Create a web app in MOSS, and in application management>content
databases you can remove the default content db, and add your content
db..

That will take you most of the way there..

You still may have to add other files  in the 12 hive and in the virtual
directory folder as well...

Assuming everything was built off of stock site  definitions, you should be OK.
You'll need to re-configure your SSP, search, and profile settings, though.

follow these steps:
1) make sure your backup  up SQL 2005 is resorted to a new
databasename if u are restoring  to the same server.
2) Create a web application if your moss installlion is up and
running else, reinstall it and get ur central admin up and running ./
3) From central admin create a web application. no need to create
site collection.
4) Go to management studio and see ur restoration is complete and
successful.
5) make sure your credentials have enough permission.
6) Form command prompt runs this command
Stsadm -o addcontentdb –url "http:\\myserver\newwebappname " -
databasename "nameofdatabase"
the process is directly proportional to DB size. Once successfully
attached.
Go to central admin again, Central Administration > Application
Management > Web Application List
Click the web application the new one and click the content database
link remove the database.
Note don't try to add large DB form UI it will time out.