Is this a PC used by an individual in a domestic environment, or a corporate one where users' profile folders would usually be on a server to which they log in?
If it's a domestic PC, then there is likely to be a lot of user-created data in the form of documents, emails, address book, photos, videos, music, and maybe other types of projects stored in the users' pfofile folders. You should be aware that it is very easy to lose that data, or at least lose access to it, if you mess too deeply.
Rebuildin the boot configuration file as Merete is suggesting will normally not put the data at risk. You are just trying to ensure that, during the system boot, it has the correct settings to boot the system to the system hard drive.
However, if you end up messing any more, you should seriously consider trying to copy out potentially important data to something like an external USB hard drive or even burning to CD/DVD. willcomp's suggestion of using the Microsoft Diagnostic and Recovery Toolset (MSDaRT) SHOULD allow you to access the profile folders for all users and copy out essential files to another hard drive, and it is something you should test out before you go any deeper should the rebuilding of the boot config file fail to get the system bootable.
I'm sure any of us would be glad to either provide a list of the places where user-specific data is normally stored, or point you to some pages that provide the information.
The last thing you want is to hand back the PC late AND with data lost. Any sensible person should grasp the importance of your efforts to retain their data, and making this the priority at the expense of a slightly further delay in returning it should be an excuse that is acceptable by most. I've had this a few times before where, despite all my best efforts to recover data, I had to admit defeat and tell the owner. It's a horrible feelin, even where you are helping a friend out of a hole, but would be even worse if the person was a paying customer.
I have used the predecessor to MSDaRT (ERD Commander) to recover data, but I have probably used a couple of versions of Linux from a Bootable "Live CD" more often. Unfortunately I cannot be sure which of the Live CDs worked best for me for accessing user profile folders and copying out files and folders, but I have a feeling the following were best for me (in order of preference from memory):
1. Linux Mint 4.x Lite
2. PCLinuxOS
3. Damn Small Linux 4.x.x
4. Ubuntu Live
5. Ubuntu Live
6. Open SuSE 10.x
Although most often suggested, Knoppix hasn't worked too great for me in some respects, but I have always try it amongst the first of my tests.
Good links lists here:
http://www.livecdlist.com/http://distrowatch.com/http://iso.linuxquestions.org/search.php?what=distros&orderby=distro_nameJust about all Linux versions can boot into their own environment in memory only without leaving a trace on the hard drive. Just check and make sure if it can boot as a "Live" CD before downloading an *.iso CD image to burn.
Seeing as you have the "Ultimate Boot CD" and can "boot the machine into a Personal environment" using it, then if you have a user interface from which you can see and manage folders, then perhaps just persevere with that. I have never yet had complete success with the UBCD, so I don't know what kind of "shell" User Interface it has for file and folder management.
