When I try to open Excel, I get an error message: Installation Error: File not found. A required installation file SKU112.CAB could not be found. Original installation source required. I don't have the origial Office 2003 installation disc as it was installed by Dell with my order. How can I correc this error?

This is usually caused by differing versions of MS Office programs on the same computer. Regardless of what triggered it, the answer is the same. You have to reinstall the version of Office that Excel came with... and for that you need disks.

Trial versions are often included with a new computer. You activated it SOMEHOW years ago when the trial ended. Only you know how you did that.

Meanwhile, the answer is the same now, you have to reinstall.

1) Contact Dell and ask for the Application Disks that should have accompanied your computer, or instructions on reinstalling original Applications
2) Contact MS and ask for installation media, since your previous activation provided you with the installation license key, now you just need disks.
3) If you used a "friends" CDs to activate your software in the past to get around the trial period, use the friends CDs again.

Regardless of HOW you got into this situation, the answer is the same... reinstall with actual product disks.

SIDEBAR - check your ADD/REMOVE PROGRAMS and see if you really do have two different versions / partial versions of Office on your computer. Part of your reinstall should be to completely eliminate the OTHER version from your computer.