Dos or Windows xp reboot

David,
That's not the right way to do it. Aduggan had it right. These days the new computer that has a 3.5 drive is a rarity. 3.5 drives are an option that most people do not bother getting.

The response before yours, made by aduggan, had it correct. Just after the machine completes its POST, but before Windows can load, you want to hit the appropriate function key for your computer. It should say which one on the screen as the system starts its loading sequence. Go into the BIOS setup interface, choose Boot and then look for a button indicating boot priority. Different manufacturers use different schemes for this. No matter; what you're trying to do is have it select the CD drive prior to the hard drive or a (if it has one) floppy drive. Once you've got that set, exit and save. The Boot sequence will start, so you should have put the CD in the drive before any of this. Watch for a message asking whether you want to start from CD or hard drive. If the system has one of those, it will default to the hard drive if you don't hit a key in the alloted time.

The next issue is whether you're repairing a system or want to completely re-install. Repairing just over-writes all the system files with known good ones. If there are viruses, trojans, and other malware present on the drive, this won't achieve much. You'll have good system files in an infected system. You'd want to go this route if system files had been corrupted or erased, and the system was known to be clean. Or if you were trying to recover user data. Hopefully, all the data has been previously backed up. I said hopefully. Don't bet the farm on it. If you have a system where it is known to be thouroughly infected and the user data has been backed up, or the user doesn't have any data that they care about, then you want to completely re-install Windows. Read the prompts carefully, this process is not fault tolerant. If you're tired, put it off until you're more rested if you can. You will want to select Install Windows. Some systems restore CD programs split it after this point; watch for the option to hit R for repair or ENTER for install. Once you've got it going, it will ask about partitions. You will want to delete the existing Windows partition and create a new one. After that, it formats the thing and then starts actually installing the OS. Plan on about 3 to 3.5 hours for a full installation, including the drivers CD, the manufacturer supplied programs and the bundled applications CD. All told, there may be between two and four CDs to install from, not including any "after purchase" programs such as MS Office, MS Money, Quicken, etcetera.

A few other suggestions:
Make sure the computer is not connected to the internet until after the system is fully re-installed AND an anti-virus program and a firewall are installed and configured.

Prior to connecting to the internet, run the antivirus program. Bad things also come in shrink-wrap, like the worm inside a certain name-brand shrink-wrapped music player.

Prior to connecting to the internet, when you are certain the machine is clean, establish a "Known Good" Restore Point using the Restore Point function.

Then connect to the net. Immediately do a Windows Update. Actually it will probably be what will seem like an unending series of updates, to get every update and patch Microsoft ever created. After doing all the SP1 level updates, but before getting SP2, perform another Restore Point and label is as SP1 Known Good. Then install Service Pack 2. Once that is done, grab all the subsequent updates and follow that with your last Restore Point of the night.

At this point, in the Restore Point history, you'll have:
Known Good (bare install)
SP1 level
SP2 complete
so, God forbid, if you have to revert to a previous level, you'll have something dependable that you can work with.

You can first check to see what is actually on the HD: by booting either from a FREE Knoppix Linux CD ( or use rawwrite to create a bootable Knoppix floppy with cd support.
You can then use the cd writer ( install one if it isn't there, and back up all the Saved work.
Knoppix will enable you to grab ANY unencrypted
dos to NTFS oartition file and burn to CD/DVD or even a 1 gig USB pen drive(now available for under ?50).
The you can google "Ultimate boot CD"
download the again FREE iso, burn to a cd.
Then boot from this cd and see if you can reair the system, assuming that the Windows XP restore
system won't work.
BTW, Knoppix allows you to grab and burn XP pro when you have lost the supervisor pwd, it also bypasses fingerprint recognition systems and most other windows based security... and leaves no traces.
I believe thet SuSe Live can do the same, but i only use the full set suse 9.3 pro myself (at ?1 a cd, for a legal copy)