I can't shrink my C: drive?

hi everyone in new on here and id like to ask why my windows 8 is acting up badly. (its been the biggest mistake i made in my life infact). I want to shrink my 450gb c drive down a little but the following occurs.
I'm a daily gamer, and have been using windows 7 ever since. I have no idea why microsoft had to change windows 8 completely. can anyone help?

Do you have bitlocker turned on by any chance? Turn it off if you do and try again - you can turn it on again after. It is the same on 7 & 8...

In addition to what Adam said above. Your HD is probably fragmented, you'd need to defrag your HD and consolidate all the free space then you'll be able to shrink.

However, it is easier if you download Bootable Partition Manger | MiniTool Partition Wizard Bootable Edition and use Rufus - Create bootable USB and boot it from the USB to resize the drive.

Free space doesn't mean it continuous free space. It will only let you shrink back to where Data is found. Like topgundcp suggested, defrag your drive and see it that gets you some more room.

Alphanumeric is correct. If the data on your HD is scattered near the end and if they were unmovable data such as pagefile.sys or hiberfile.sys then even running defrag will not move them unless you're running it offline. So your best bet is to use Minitool Partition Wizard offline from bootable USB.