You can always manually create a Restore Point.  Right-click on Computer, Properties, System Protection (link on the left), then Create....

When you're ready, just go here and follow the instructions:
https://www.microsoft.com/windows/virtual-pc/download.aspx

There are three downloads (updates), but you only need the third one if your processor does not support Hardware Assisted Virtualization (or VT on Intel chips).  If you have questions on whether your processor has VT or not, let me know and I'll tell you.  Note:  If your processor does support VT, you will need to turn it on in the BIOS (F2 Setup on startup).

Processor Model Dell Optiplex 780USFF

Processor Intel Core2 Duo CPU E7500

I need your processor model/description :)

System Properties:
Right-click on Computer, Properties ... may be listed under System.

Device Manager:
Right-click on Computer, Manage, Device Manager ... listed under Processors.

As you offered, please tell me how to find out.  thanks!

The E7500 is equipped with VT, so you will need to first boot to the BIOS Setup (F2) and enable VT/virtualization.  Then just install the XP Mode, then the Virtual PC updates listed on the Microsoft page I gave you a link for earlier.

Proceeded as you advised. "Enable VT/virtualization" box was already checked. So now I'm ready to go.

Many thanks for your time and help!

No problem ... glad it worked out.