Not sure exactly what you want to do. The 2400 never shipped with Windows 7, so if you were given this with Windows 7 on it, it is not legit if you didn't also get a product key (license) with it.  My guess is they loaded Windows 7 without activating, which gives you 30 days before it requires you to activate it. All versions of Windows create a Windows.OLD folder when installing to a partition that has a Windows installation on it already (if you choose not to delete/format that partition).  If you want to restore to that XP installation, here is a guide that may help: support.microsoft.com/.../933168 Since this system's license (if it is indeed still intact) would be for XP, if you have a Dell XP disk, I would strongly advise skipping the Windows.OLD fix and do a fresh install of XP from the disk (deleting and formatting the existing partitions, of course).
Hello (first post!), Recently I was given a Dimension 2400 with, I think, a 40 GB drive.  It had Windows Seven Ultimate on it, but I quickly found out it was not genuine (screen went black, etc.) I replaced the stock PSU (wouldn't boot) with a good one (new OCZ Fata1ity 550W) and now it boots every time.  (I'll do a BIOS upgrade and a 2.8 GHz Northwood CPU upgrade later today, I could do a video card upgrade at some point.)  This will be a great file server, backup manager and network learning experience. (And if I haven't nagged you yet, it is because this is my first post.  BACK UP YOUR FILES.  BACK UP YOUR FILES.  BACK UP YOUR FILES LIKE YOU SHOULD.  There.  I just had to get that over with.) There are quite a few files (it looks like a whole Windows XP installation) in the directory WINDOWS.OLD.  Can I delete the WINDOWS directory (where Seven resides) and rename WINDOWS.OLD to WINDOWS?  This model originally came with XP, and since I don't have any Dell disks or recovery partitions, I could get a few more years out of this computer. (I think Windows 98 put old Windows installs in WINDOWS.OLD in case we wanted to revert to the previous version, I suspect that has happened here.) What else would I need?  Is the swap file in the root directory?  Do I need to fix the MBR so XP will boot?  Would any needed files be the same as the OEM XP disk I have (used legally on another machine)? Thanks in advance!
Removing Win Seven Ultimate