Windows XP Pro. 80GB hard disk.
Suddenly, the disk usage went from about 23GB to 74GB and warning messages showed that disk capacity was nearing max.
Showing only about 24GB of programs etc. loaded. Cannot find what else is on the disk, which is clogging it up.
Any help appreciated.
Fred
fdiba2@gmail.com

two obvious ones come to mind:-

1) have you got a massive page file newly created - could be if you have been editing video or similar and ran out of RAM when doing it ? I had a similar problem on one of my drives recently, editing a ridiculously large bitmap file. If so you need to delete it.
2) have you hibernated the system - Windows does not like delelting hiberfil.sys, and can usually only be persuaded to do it from either Safe Mode, or Safe Mode command prompt ?

Thanks, but no to both suggestions. Neither a large page file nor hibernated.

I assume you have gone to the control panel and marked "show hidden files and folders" in Folder Options.
If you are still unable to see what the 50 GB has in it, then you need to look at the disk in DOS to determine what has appropriated most of your disk.
There is an NTFS Reader for DOS [freeware] at this link:
http://www.ntfs.com/products.htm
This should let you see what is in that 50 GB area
Good luck.

There is a better way to do this : v-com powerdesk has a powerfull feature letting you  to read in detail the size of anything (folders and files )on your HD ; you do not need going to DOS ; everything is present in a nice interface. The counterpart is that it is shareware not freeware ; i use it since the beginning when Ontrack crested the tool ; I never worked since without it ; powerfull, pleasant , and superefficient .
This beeing said , I have a guess : your system is creating HUGE restore points ; try to apply the former tips about options for files anfd folders ; let uncheckecked the option for hiding system files and hidden files; you should discover a folder "System volume INFORMATION ", develop it and get its total size ; you will discover a tremendous amount of restore points whith the size of each on the disc . use windows cleaner tool to get rid of the old restore points , just saving the newwest one .   OLIVIER GEBUHRER