Ubuntu – increase the hard disk space in virtual box which is running Windows 7 currently

hard drivepartitioningvirtualbox

I have my first attempt to install an OS using virtual box and for that I made a 25 gb partition to my hard disk and now I want to increase its size. Is that valid, and if yes, how can i do it?

This is the current status of my virtual machine. I have another question regarding 3d settings for Windows 7 which is installed in virtual box.
can virtual box support 3d games

this is shown when i type the given commands in terminal

VBoxManage modifyhd "/home/agha/VirtualBox VMs/agha rehan abbas/agha rehan abbas.vdi" -–resize 60000 (size is in MB)