Keep getting "Not Enough Space On The Disk" when trying to save files to a server share?

I am using a number of shares set up on my SBS 2003 Server and I have set the permissions as Everyone with Full Control. I have got an XP pro box logged into the domain and when I am trying to save a file to the shared folder then I am getting the following error "Unable to create the file "abc.txt. There is not enough space on the disk". The disk is actually having more than 150gb free space. I have checked the permissions and they all say that I must have permission to write files to the folder. When I checked at the top level shared folder I found at the permissions in the share that was having:
Administrators - Full Control
Everyone - Full control

Also, the Security tab shows:
Administrators - Full control
CREATOR OWNER - Special Permissions - inherited
Domain Users - Full Control - Inherited
Everyone - Full Control
System - Full Control - Inherited
Users - Full control - Inherited.

So, I dont understand why I am getting this error? Any suggestions would be welcome.

I think that the quotas on the partition/volume is where the user shared folders are. By default, it is set to 1gb per user, and over the entire drive, not counting exchnage, sql or sharepoint. Try to follow the below method to fix this issue:

1. First of all log on to your system with an administrator account, like, owner or administrator.
2. After that you have to click Start, and then click My Computer.
3. Now you need to right-click on the drive, and then click Properties.
4. After that click the Quota tab.
5. Now here you have to either increase the amount of disk space available to users by changing the Limit disk space to option or disable the Disk Quotas feature by clicking to clear the Enable Quota management check box.

That worked instantly, thanks for the exact solutions for the problem that I was facing.