I installed a new solid state drive (SSD) pre-loaded with Win 7 Home Edition OS and my program files in the primary bay of my laptop . I plan to use the original HDD in the second bay of my laptop for data files. I had to clean out all the OS-related files and folders from this HDD and leave my existing data files intact.
I installed the HDD in the second bay of my laptop (it could be left outside and connected via a USB port) and tried to delete the OS files with Windows Explorer. The running Windows OS would not let me delete the system files. I tried several ways of changing permissions and none of them worked for me. So, I used a program called "PartedMagic",. The PM program gets loaded via a CD on power-up, before Windows boots, so Windows cannot invoke it's rules against deleting System Files.
Here's the short procedure: Download the PM program, save it, and burn it to a CD. Insert the CD and reboot the computer. Set the BIOS to boot from the CD. Among many other things, PM has a "Windows Explorer" like feature. Open it, navigate to the correct HDD and delete all the files and folders related to the OS. While you are there, delete any other unwanted folders and files. Defrag the HDD and your done.
Details left out of the short procedure:
Insert the CD created above into the CD tray and close it. Restart the pc. When the pc starts to boot up, press the ESC key (or f10 key) repeatedly to enter the BIOS. Set the BIOS to boot from the CD. Select "1", the default setting, on PM. After the program has loaded, click on the "Explorer" icon. Select the HDD you want to work on and start deleting. When you think you have removed all of the "undeletable" files and folders you "might" be done. Restart your computer. It should boot to the installed OS. If not, remove the CD and try again. Take a look at the HDD contents with Windows Explorer. You can delete unwanted non-OS data with WE.
OR,
I used another neat program that runs in Windows called WinDirStat to do a final clean up. Download and run the program. Select the drive you are working on. This program presents a great visual display of the HDD contents. Note: be patient, it takes WinDirStat a few minutes to crunch the contents and display it. Navigate around the colorful display and, when you are done deleting, run a defrag program. You are set go with lot's of space to store your data.
P.S. Please don't interpret anything in this procedure as disparaging toward Microsoft products. I like Windows 7.
takeown /F D:\Windows /R /A /D N
and thenattrib D:\Windows\*.* -S /s