CHKDSK: USN Journal Error

Q: Everytime I run scandisk, always getting bellow error:

39 percent complete. (XXXXXXXX.. of XXXXXXX.. USN bytes processed)
..
..

Where XXX.. is a number eg. 97517568 of 104914048.
Maybe the amount of the list around 40 - 50 list.

I suggest that you back up all your data and be prepared for a reformat and reinstallation.

If you're getting something like this:

CHKDSK is verifying Usn Journal...
36040912 USN bytes processed.
Usn Journal verification completed.

that's normal.

See Here.

The USN is the Update Sequence Number, if the USN journal is corrupt you may need to reformat and reinstall Windows.

You could try the Recovery Console and run chkdsk /r from there.

If you have Norton Utilities (includes Scandisk) or a similar utility, it may be worth trying a repair.

TuneUp's Disk Doctor would certainly be worth a try.

Q: What'll happen if I don't fix this error right now?

Quite possibly nothing will happen. It's just something to keep in the back of your mind. That there is a corrupt part of your disc and at some stage that may come back and bite you. As long as you keep regular backups of changed data you could continue indefinitely as is. The unallocated space wouldn't be causing this. You can use Disk Director to increase C:\ using that space.

It's likely that you just have corrupt files, but sometimes that's an indication of hard drive problems. Backups won't make it go away. To be safe, I would reformat at the first opportunity.