Click Start, Run, type diskmgmt.msc and press Enter.
In the bottom half, you should see Disk0 which should be your old hard disk.
Below that you should see Disk1 which is your new disk. Right click Disk1 and see if you need to initialise the disk. [If you see that option, you need to, just select it].
Otherwise, if you see an opotion to Create new partition. Select that. Then follow the prompts to create new partition, then format it. Wait for formatting to finish, until you see "healthy". Then exit Disk Management, go to My Computer, and you should be able to see and use the new partition.