If I upgrade my HP hard drive from an 80 gig to a hitachi 3tb do I have to upgra

I don't know the exact details, however I think there are PROBLEMS when installing a 3TB drive as your main Windows drive as I think it may not be recognized.

It's my understanding that a 2TB drive is the limit for most computers.

You can Google this further, however my advice is to buy a FASTER, SMALLER hard drive for Windows and use a 2TB or 3TB as a SECOND hard drive. It's a good idea anyway to have a second hard drive for:
- Windows Images (I use Acronis True Image and create a DAILY, incremental image of Windows. Western Digital has a free version if you have a WD hard drive which allows manual backups which I STRONLY recommend in case of a failure. Say, once per week and delete all but the LAST four backups.)
- Media files
- Downloads
- Games (only if you have limited space by using a small, but fast SSD such as the 120GB Vertex 3)

Here's what I recommend:
- find a store with great prices, like NCIX online
- buy two drives:
a) Western Digital 500GB BLACK
b) Western Digital 2TB GREEN

Installation:
1) Download and install the Western Digital diagnostics
2) shut down your computer, install the 500GB drive and start your computer
3) run the best diagnostics option to fully test the 500GB drive
4) Install the WD Acronis True Image software (contains CLONING software)
5) CLONE your old drive to the new 500GB drive
6) shut down your computer, REMOVE the 80GB drive and replace with the 2TB drive
7) start, and run full diagnostics for the 2TB drive
8) create a "Windows Backup" folder then run Acronis True Image and create a backup Image of Windows (in case of hard drive physical failure or software corruption you can RESTORE this backup)

I hope this helps!