Windows 7: format win7 hard drive and reinstall win7 Home Premium.

I have a Dell Laptop which came with XP, last year I purchased Windows 7 Home Premium Upgrade and installed it on the Laptop. I let my stepson use it until today, the User files have been messed with and there is more junk on it than I am willing to work around.
I would like to format the hard drive and reinstall Windows 7 using the same disc I purchased last year. I still have the Product Key.
I have searched but have not found details particular to my needs, which basically means I am no Techie!

I believe you will find this is what you are looking for.
Clean Install with a Upgrade Windows 7 Version

The system will run much better in general using that method rather than upgrading as well.

You'll save a lot of time updating if you use the latest installer with SP1: Win7 Home Premium x64 SP1 English Official ISO download

Burn to DVD or write to flash stick using Windows 7 USB-DVD Download Tool

Then adapt these steps to get a perfect clean reinstall: Reinstalling Windows 7

When you boot the installer to reinstall, it will see the OS on the HD and allow use of Upgrade version Product Key during install - even if you go on to use Custom>Drive options to delete, repartition and format before install.

I am really confused, I downloaded the Windows 7 USB-DVD Download Tool to my desktop. I clicked on Windows 7 Home Premium x64 SP1 English Official ISO download to download it to my desktop and it says it will take 6+ hours to download.

What am I doing wrong?

You may want to find a faster connection to download ISO.

You are not doing anything wrong. You probably have a slow speed connection but twice as fast as my connection. For me it took something like 12 hours to download it. Six hours is almost half that time.

Leave it to download overnight.

After hours of being confused I put the Windows 7 disc in the drive, shut down the laptop and started it up, following the prompts, including formatting, and Win 7 loaded and I have a new start.
Sorry I could not follow all the confusing information posted.

You might want to try asking a question or two if you're confused, instead of just complaining.

One quick question unrelated to the initial topic. Is that download file 100% safe to use? I know that downloads of cracked software can sometimes have stuff thrown in with the crack like spyware etc, that's why I ask. Also i phoned my computer shop recently to ask them to make me a vista disc if I showed them the serial number on my pc, but they said it's illegal. This seems the same thing. I'm not trying to be funny here, asking a serious question.

That is the official Windows 7 ISO download from Digital River which is the MS fulfiller of Student Upgrade special.

I provided it so you wouldn't have to get one from a torrent or other sketchy source.

This is the top tech forum on the web with some of the tightest standards on piracy of all. We waited longer than MS's own tech forums before being allowed to link to the official Windows 7 downloads.

If you have a license and you need to reinstall Windows 7 then what would be illegal about it?