If Windows seems corrupted or needs to be reinstalled, you may be able to reinstall it easily. Try these steps:
Restart the computer in MS-DOS mode. You should get to a C:\Windows> prompt. Type in CD\ and press <Enter>. From there type in ZZTOP and press <Enter>. If the ZZTop program starts, choose to Restore The Factory Image. The system will check to be sure that the old image is still good. If it is, you can choose to continue and it will automatically format your hard drive and reinstall everything on the computer just like it was the day that you first turned it on. If you get an error message similar to invalid dump file, then the old image is not usable.
You can put Windows XP on it if you want. It meets minimum requirements. For performance reasons, with a 500MHz processor, you might want to increase the memory to 512MB.
That particular model is a solid, stable and reliable system. Upgrading the hard drive and RAM will give you a good platform for most of your photo editing.
It will have to be networked in order to use it as a file storage system.
Oh boy, this forum use to be full of upgrade info for XPS T400 to T700. It's probably all gone now. This is where I learned all the possibilities of what could be done. I am having trouble remembering specs but here goes.
Dell Dimension XPS T__ User manual:
First and foremost is to update the BIOS. If you don't, it's quite possible nothing will work when you install the components. Also, do one upgrade at a time. See if it works each upgrade.
BIOS for XPS T___
MEMORY: It's quite easy to get the memory. Your DELL manual will tell you the specs of the memory and what the maximum is. However, if you go to the "Upgrade My System" portion of the Dell support site, it will list all available components for your system. Also, sites like Crucial will have memory configurators.
Dimension XPS T__ memory available at crucial: