Expanding Partition Size for Windows

Question

I used Bootcamp to set up a partition on my computer for Windows, and spent some time tweaking... and then found that I was nearly out of space when selecting a 40GB partition. So as much as it pained me to do so, I deleted the partition, and then tried to start all over. But now, on that screen of the Bootcamp setup, it won't allow me to specify a partition larger than 44GB, and as you can see from the screen shot below, I have plenty of excess capacity on my computer (after deleting several things, emptying my trash and rebooting).
Any ideas on why I won't "slide" any further?

Answer 1

I'm afraid not. The easy way is to make a bootable backup of your hard drive. Boot from the backup, erase the internal drive, then restore the backup from the backup drive. The tool for that is Disk Utility.
Clone the internal drive to an external backup drive.
Boot from the Recovery HD on the newly made clone.
Erase the internal drive.
Restore the clone to the internal drive.
Clone Yosemite, Mavericks, Lion/Mountain Lion using Restore Option of Disk Utility
Boot to the Recovery HD:
Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.
     1. Select Disk Utility from the main menu then press the Continue
         button.
     2. Select the destination volume from the left side list.
     3. Click on the Restore tab in the DU main window.
     4. Select the destination volume from the left side list and drag it
         to the Destination entry field.
     5. Select the source volume from the left side list and drag it to
         the Source entry field.
     6. Double-check you got it right, then click on the Restore button.
Destination means the external backup drive. Source means the internal startup drive.
Boot Using OPTION key:
  1. Restart the computer.
  2. Immediately after the chime press and hold down the
      "OPTION" key.
  3. Release the key when the boot manager appears.
  4. Select the disk icon of the external drive's Recovery HD.
  5. Click on the arrow button below the icon.
When the Utility Menu appears select Disk Utility and click on the Continue button. Select the OS X volume on the internal drive from the sidebar list, click on the Erase tab in Disk Utility's main window, set the format to Mac OS Extended, Journaled and click on the Erase button.
Restore the clone
     1. Select the destination volume from the left side list.
     2. Click on the Restore tab in the DU main window.
     3. Select the destination volume from the left side list and drag it
         to the Destination entry field.
     4. Select the source volume from the left side list and drag it to
         the Source entry field.
     5. Double-check you got it right, then click on the Restore button.
Source means the external backup drive. Destination means the internal startup drive.