low disk space error in windows xp when I know disk is less than 1/3 full (back up drive show that much free space), I've run virus scan, rebooted, unplugged, to no avail. Help.
You could go to disk management (right-click "My Computer"->"manage"->"storage manage"->"disk management")
Then it will list all the infomration of your partition on the disk map, you could view the free space of every partition. If the system partition nearly to running out space but the data partition contains a large numbers of free space, in windows XP you need some partition software, such as Partition Assistant Home Edtition which is free to resize your partition, this article solve low disk space
would give you some help.
However, if the low disk space is not on partition but on hard disk, then you need to upgrade your hard disk (buy a larger hard disk, then clone the old HDD to new HDD).