Stop Excel 2003 files opening in separate instances

[Gavona]

If I highlight several excel files in a folder, right click and select Open each opens in its own instance of Excel. (NOT just windows, separate instances).

To solve this I have tried the following but ot doesn't work for me:

Close Excel and
Windows Start Button|Run
excel /unregserver
then
Windows Start Button|Run
excel /regserver

The /unregserver & /regserver stuff resets the windows registry to excel's
factory defaults.

I guess the unusual thing about this machine is that it came with Office 2007 installed. I installed 2003 over the top.

Any ideas please?

Gavin