Thank you all for your input. I've decided to stick with 2003 on the desktop and one laptop, loading 2007 on the other laptop should I need it in future. I removed 2007 from the desktop, but then Outlook 2003 wouldn't co-operate. Changed MSmapi32.DLL to MSmapi.old and it worked like a charm.
For 2011 I'm going to be using an external hard drive for backup and working with an 8gb flash drive so I have everything to work with on any computer, anywhere, any time.
Oh the joys (and frustrations) of technology!
Lynne