That's the problem, the pre-installed OEM version can't be downloaded from a legal source forcing folk to buy Recovery Disks from Manufacturers. I prepared a step-by-step System Image Recovery (8.1)yesterday for someone else. should be OK. It includes the recovery procedure.
Require
USB Pendrive/Ext Drive/Separate Internal Drive greater than ‘C’ Drive or several blank DVDs
Small USB Pendrive (1 Gb) if you have no Installation Media
At Start Screen -
Search for ‘File History’
Select ‘File History’
System Image Backup (Bottom Left)
Select backup media
Create Image, include System Reserved Partition,then, if no Installation Media, create Recovery Drive
At Start Screen –
Create Recovery Drive by typing ‘Recovery’ select ‘Create a Recovery Drive’ (Require 1Gb USB Drive)
To Restore System
Boot from Recovery Drive/Installation Media
(Choose ‘Repair’ if Installation Media)
Choose Language and progress through Troubleshoot and Advanced Options to Restore from System Image, insert Final Disk of Image or USB drive when prompted and click Retry.
Your Backup Disk details should appear.
Click Next
Leave Format unchecked if it’s a new disk then click Next
Click Finish to proceed with Restore