Shouls i wipe my hard drive clean?

There's no good reason to take extraordinary measures to erase the drive.  In this specific case, I would not recommend using CCleaner's Drive Wiper feature to sanitize the free space.  Because the contents have already been erased, the entire drive is free space, and consequently CCleaner would have to write to 99.999% of the capacity, which would take a exceptionally long time.

If you are keeping the drive...there is no reason to erase.

That's your call. You know what was on it and unless you fill that hard drive up some remnants of what you had on that drive will remain. If you want to remove all data that was on it then you do need to wipe it. A free program that will do the job is CCleaner. You can get CCleaner at download.com for free. Once you install CCleaner go to the TOOLS icon and click on that. Then select Wipe and select Unused Space and click on Wipe. It's pretty much that simple. However, depending on the size of the hard drive the wiping process can take several hours. I recommend you start the Wipe process as the last thing you do on the computer for the evening and let the computer run all night performing the wipe. Hope this helps.