i recently tried to back my hard drive up, useing nero software, i kept getting messenges, saying compressing of files not completed successfully, unable to compress successfully., when it finished it said, all system files not backed up, i don't know what the problem is
Problem one is trying to use Nero to backup your system. I like Nero for many things, but I can't say system backups are one of them.
If you have the means to buy software, I do like Symantec's Norton Ghost program. Has always served me well in the past.
Windows XP has a rudimentary backup feature that does work, you'll find it in the system tools menu. Make sure you have a large backup device.
There are also a number of freeware utilities to backup stuff. I haven't tried many of them, but they could be worth a shot.