For one thing, your colleagues will be surprised at how much quicker their computers will be once you install a fresh version of Windows.
(It seems unlikely that a seven-year-old PC won't have a DVD drive, but if not you will need a bootable USB drive.) Once again, check that all files and folders have been copied to an external hard drive, USB thumb drive or a cloud storage service.
Here’s a trick to turn Windows XP Home Edition to Windows XP Pro, from within the operating system without going through installation.
This doesn’t install or add all the features from Windows XP Professional, such as Remote Desktop Server (Install Remote Desktop on XP Home) and Group Policy Editor (GPedit) utility tools, which was removed from Windows XP Home edition.
Encourage your colleagues to back up their email inboxes, and export internet bookmarks and other settings that they want to keep.
You will get pain from this, so aim for the least pain possible.