Possible fix is a new hard drive and OS?

[Caution Hot]

My computer crapped out more than 5 months ago. I kept having the computer restart randomly or blue screen on me during the night with hard drive errors. Then suddenly one day it would only load the windows 7 screen and freeze/restart. If i tried F8'ing to safe mode or going to the advanced boot options it froze and then restarts. Now 5 months later i go to start it up and i can go into a dell testing screen. i ran a extended test for a few hours and the only error that came up was the Hard drive was giving a error which i expected.
Specs:
Some dell tower that i bought more than 4 years ago through dell. I usually ran it 24/7 for most of its life. It mostly ran programs overnight but wasnt very cpu intensive programs. I kept it clean and cool though as the room was a/c in the summer to 19-21c and the same temp in the winter. i dont remember the video card specs.
2.6ghz quad core (intel i think)
750gb seagate baracudda HD
4gb ram
windows 7

So now knowing the HD is bunk i am going to get a 1tb seagate HD(cant find a 750gb instock), and windows 7 OEM. If this doesnt work out then ill just use the new HD and OS on a basic tower from the shop that comes without a OS for cheaper. Am i correct to think this is the best way to fix my computer?

 

[BPTMatthew]

If your PC has a COA sticker on it with the Windows 7 code, you should be able to re-use it on the same PC with a different hard drive.

It sounds like all you need is a new hard drive and you should be good to go

 

[Caution Hot]

Ah yes it does! thank you so much you just saved me has the product key right on the top.
So once i get the new HD i can then boot windows from a usb stick using the correct iso and windows 7 download tool. Just want to make sure im not missing anything,