<p>Is there any way to import a database backup from 2005 into 2008 express edition. What I've had to resort to is doing a script the database, then import all the data through DTS. Whenever I tried to import straight from a backup file it says something about not being to import into a new version of sql server or I'll get the below error.</p>

<p>title: Microsoft SQL Server Management Studio</p>

<p>Specified cast is not valid. (SqlManagerUI)</p>

SQL 2005 backups should be restored on 2008 without problem (have done that myself many times). What exact error message did you got about versions?
The other error (Specified cast is not valid) seems to be Management Studio error, not server error. Have you full rights on 2008 server?
Look at this question -
any-reason-to-have-sql-server-2005-and-2008-installed-on-same-machine
- there are talked both about restoring SQL2005 backups and about attaching SQL2005 data files.
(Of course you cannot attach production databases. To attach non-production databases just detach them, make file level copy of these and attach copies to new server. Orginal files need to attach to original server too :))