If you need to troubleshoot/repair the computer, you may need to create this CD to ease for you to solve the problem.
Windows Version
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This project include many free hardware and software diagnostic tools that allow you to fix almost any problem you will face with your computer. With network support, the ability to modify NTFS volumes, recover deleted files, create new NTFS volumes, scan hard drives for viruses, etc. this project includes almost everything you need to repair your system problems.
I like the feature which can reset my Windows account password when I lost it
www.ubcd4win.com
(require Windows CD to create the bootable CD)
Dos Version
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There is another Dos version bootable CD, with a lot of tools also
www.ultimatebootcd.com
(have iso format, burn directly to the blank CD)