How can I change the size of the X: drive?

Write the Hiren's BootCD PE ISO file to your USB flash drive. Let's assume that it is on the E: drive and you want to decrease the size of the X: drive within Hiren's BootCD PE to 3 GB (3072 MB).

Before starting Hiren's BootCD PE (within the normal Windows platform), you can launch cmd.exe as an Administrator and run the following commands, customizing them according to your needs:

mkdir C:\hbcd_pe

dism /cleanup-wim

dism /Mount-Wim /WimFile:E:\sources\boot.wim /index:1 /MountDir:C:\hbcd_pe

reg load HKLM\HBCD_PE_HKLM C:\hbcd_pe\Windows\System32\config\SYSTEM

reg add "HKLM\HBCD_PE_HKLM\ControlSet001\Services\FBWF" /v WinPECacheThreshold /t REG_DWORD /d 3072 /f

reg unload HKLM\HBCD_PE_HKLM

dism /Unmount-Wim /MountDir:C:\hbcd_pe /Commit

dism /cleanup-wim

rmdir C:\hbcd_pe