In effect, the method you outline should in theory work: image, break RAID, reimage.
Windows won't even require re-activation, because only the hard disk will change.
However, theory doesn't always work.
I assume your RAID-0 is pure software, so there won't be any BIOS changes.
You can use any partitioning product to reallocate the disks, although it might turn out to be simpler to just quick-install a vanilla XP, to be over-written.
Be prepared for the case where re-imaging will be impossible for one reason or another, so for a full installation of Windows. Ensure that you have all the serial numbers required to re-install all your installed software including Windows and that you have other backups in addition to the disk image.
I would also backup, just in case, all installed drivers by a product such as Driver Magician Lite.
The product I would recommend for imaging is Paragon Backup and Recovery Free, as it's the only one I know that supports Restore with Shrink, assuming that disk-space considerations will allow the restore of your two striped disks into one C: disk. It's also a partition editor, so it can create your partitions.
I would suggest before creating the image backup, to minimize disk space by clearing out all temporary files, emptying the Recycle Bin, turning off the page-file and disabling hibernation, so as to minimize the required disk space.