|As above you need to save off data if you can.|
You have to follow the directions that came with your computer. Some require you to make your disks. Some can be returned to OEM state by booting and then pressing F10 or so. Some can be recovered by using a windows programs that may be found on the all programs menu usually under the company name. (if gateway then look something like that)
The owners manual ought to be on their site also.Usually in PDF forms.
Some restores can save your current hard drive. All might be stored in a file called backup or such.
Playing to the angels
Les Paul (1915-2009)