[dba-SQLServer] My database is slow

I had a SQL Server 2005 (I think) database, running in SQL Express.  It was "fine", no obvious slowdown.

I wanted to be able to access 2008 databases and was unable to do so using Management studio 2005 
which I had installed.  I tried to "upgrade" but 2008 just refused to cooperate.  I ended up 
uninstalling all of Express as well as all of 2005 whereupon 2008 decided to cooperate and installed 
just fine.

Now my billing database is abysmally slow.  As in 20 seconds to open any table.  Sometimes. 
Sometimes not.  Buy just loading the combos that used to open instantly is now taking literally 20 
seconds.

This is unusable, and I don't know where to start in figuring out why.

Any ideas where to start?  In DETAIL (I am not a DBA).

-- 
John W. Colby
www.ColbyConsulting.com