What is this unknown space on my hard disk-WindirStat

[danielsaid]

My laptop has 37.3Gb of space. Not alot, but I mostly use it for word and email. Windows somehow ate 18.8 gigabytes (as shown by WindirStat,)
but there is no other major source of space-wasting. I checked "unknown"
in the options of the WindirStat program, and suddenly a giant yellow square appeared in the graphic tree proclaiming that "unknown" was eating 7.2 gb.
How can I get them back?
windows Defragmentater won't run because it doesn't have enough space, but I barely have 2 gigs of my stuff! Can I clean out the unknown part which
I don't think is a partition?

 

[Pyree]

delete restore points to reclaim your space.

 

[crisso2face]

its a backup partition used to resore yore sistem to factory default. depends on brand to barnd for each laptop what is the buton combination for accesing the restore function on sistem startup, but usually is F8, F12, things like that. The ideea is, " DONT DELETE THAT PARTITION", or you will lose the posibility of factory default. These means restoring windows to its previous state since the laptop was saled to you.