Drive X: is small.

[Steve2926]

You must remake the boot.wim file to increase scratch space if that is what you mean?

Open a CMD prompt as an Administrator.
Use DISM to mount the boot.wim:
DISM /Mount-Wim /WimFile:C:\Mount\Boot.wim /index:1 /MountDir:C:\mount\bootwim
Use DISM to increase the Scratch Space (This example increases it to 256MB):
DISM /image:C:\mount\bootwim /Set-ScratchSpace:256
Use DISM to commit the change, and unmount the image:
DISM /Unmount-Wim /MountDir:C:\mount\bootwim\ /Commit

Use Google to find more details

Why would you need to increase X: free space? If system has over 1GB then X: is 512MB. with over 500MB free.