Win8.1 OS (C:) partition refuses to shrink!

[m654321]

"Invalid signature detected.

Goldfinger said: Check Secure boot Policy in setup".From what I've read, Win 7 should be installable in UEFI mode, but under a few conditions:

• It must be a 64-bit version
  
• It must be a full "Retail" version of Windows; or an OEM version that was already installed to that particular computer in UEFI mode.  If it's an OEM version that was installed to computer in CSM/Legacy mode, it must be installed as it was originally.  If from a different machine, it won't work either (maybe not in any mode).
  
• The hard drive needs to have a GPT partition table on it before you attempt to install to it.  Windows (7 and above) will install to the drive based on the type of partition table it detects on the hard drive.  Windows will only install in Legacy mode if it detects and MBR drive.  And it will only install in UEFI mode if it detects GPT partitions
  

My reply: yes, sorry, I explained poorly in the last post. Win7 was installed from a virgin OEM DVD, laptop booted from DVD in 'UEFI mode' though the firmware was set with fast boot and secure boot both disabled. In booted fine in legacy mode. However when I put the firmware settings back to fast boot & secure boot enabled, when it rebooted it got stuck at a red screen with the message. Yes the disk was GPT etc... 
"Invalid signature detected. Check Secure boot Policy in setup".  That led me to thnk that UEFI is not backwardly compatible with an OS that's earlier than the one the laptop came preinstalled with, though of course I might be completely wrong here.  Anyway, enough of my brief flirting with win7.
I've now returned to the problem of binding in the dual boot UEFI set-up I have for LL2.4/win8.1 - see latest in that thread.  Under Gparted, I notice that sdb (GPT, ntfs formatted), for the DATA partition, has a msftdata flag - maybe  protected by windows from any other OS trying to get at it??? In the good fully functioning copy that I have of the UEFI dual boot (fast boot & secure boot enabled), that I didn't attempt to install binding on, it works amazingly: the grub screen comes up almost immediately and both LL and win8.1 load from the grub menu in less than 6 seconds!  It's the binding problem that's driving me absolutely crazy...  I am still going to work on this but await further feedback from you on next steps...  I wondered if you could reply on that thread for the binding, so that everything is kept together in one place.  Many thanks
Regards
Mike