I'm running a dell 3100 with windows XP professional SP3. I have been using without any problems the NTBACKUP program provided...until today. All of a sudden it has stopped working. I can see it as a process in the processes tab of Task Manager, but it is not in the applications tab. I have recently installed Office 2010, but NTBACKUP was working after the install so I do not believe this to be the problem. I've searched the web for some answers but most want you to download and install the NTBACKUP.MSI file, which I have done. I do not have the original OS software as XP was installed on the computer at purchase. Any help out there?

Not help exactly but an observation!, In many recent programs (eg win 7,office etc) you get a range of programs from student through home to professional etc). The ability to do backups using the internal backup system to any drive other than C: does not work in some of these programs (depending on the version you have). One then has to use an external program that will back up to an external drive. It may well be that your version of XP is showing its age and not able to cope with some later programs because of this type of restriction.
Hope you find a solution but probably depending on the machine an update to the OS is due!