My family PC has Windows Vista and lately it has became unusable, having strange errors and taking hours to do anything at all, so I'm installing Ubuntu 11.10 alongside it. I went into GParted to resize the Vista partition but found that it had an exclamation point in a red circle next to it:

I tried to resize it but the Resize/Move button was grayed out. I thought that this might have to do with the exclamation point so I looked at the information and found a load of errors:

What does the exclamation point mean? How can I resize my partition?

UPDATE 1

I booted into Safe Mode with Command Prompt in Vista as suggested by eug and ranchkdsk c: /F /R (/F Fixed errors on the disk, /R Locates bad sectors and recovers readable information) and got:

Chkdsk cannot run because the volume is in use by another process.  Would you like to schedule this volume to be checked the next time the system restarts? (Y/)

When I reboot it doesn't run chkdsk, I'm selecting Safe Mode with Command Prompt again because I can't boot normally. How can I stop it being used?

UPDATE 2

I tried doing what Luis suggested. Here is the terminal output:

ubuntu@ubuntu:~$ sudo ntfsfix /dev/sda3

Mounting volume... OK

Processing of $MFT and $MFTMirr completed successfully.

NTFS volume version is 3.1.

NTFS partition /dev/sda3 was processed successfully.

ubuntu@ubuntu:~$ sudo apt-get install ntfsprogs

Reading package lists... Done

Building dependency tree       

Reading state information... Done

Note, selecting 'ntfs-3g' instead of 'ntfsprogs'

ntfs-3g is already the newest version.

0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.

I still cannot resize the partition. Ntfsfix doesn't look like it did anything and ntfsprogs is already installed. I can access the hard drive and do backups with the Ubuntu Live CD which I'm using now. Any other suggestions?

UPDATE 3

I attempted to use the ntfsresize command but I got an error:

ERROR: Volume is scheduled for check.

Run chkdsk /f and please try again, or see option -f.

This is because I ran chkdsk in Vista Safe Mode with Command Prompt and it couldn't do it because it was in use but offered to do it at the next reboot. I reboot and I get to the menu to the menu to choose whether to Start Windows Normally, Safe Mode, etc instead of checking the disk. Is there any way I can unschedule?

EDIT

I just found out that I could use the -f option to force it. It failed and told me to run chkdsk /f in Windows and then reboot twice. But the chkdsk program is in the partition I am trying to check so it says it is in use.