Windows 7 installation - which partitions can I delete?

My computer is knackered and I want to wipe it clean and start again. I don't want to keep ANY of what's on there as it had a virus that corrupted my internet explorer and I want to fix it. I have backed everything I do want up onto disk already.

So I'm installing windows 7 custom installation from rebooting it as it says, but it gives me options to format or delete 3 partitions: 1 is a reserved small space (~1.5GB i think), the other is the vista operating system (~55GB), the last is a data partition (~50GB). So now I don't know which I can and can't delete in order to clean my computer completely, yet still have it working and working via windows 7! What is the difference between formatting and deleting anyway, will formatting clean my explorer of the virus it had?

Any suggestions? THANK YOU!!! :)

Do you have a Win7 DVD? Is it Upgrade or Full Retail?

As you have a virus, you really don't have much choice but to deep clean the HD to be sure you are clean. Use the Diskpart commands given by Jonathan above using the Win7 DVD. Then boot back into the DVD to do a Custom install, using Drive tools to Create New partition(s) as you wish, format before installing to first partition.

If you haven't made your Vista Recovery Disks, you might want to do that if you want a path back to Factory condition for later resale or servicing of the computer. Be sure to scan the disks for infection after making them.

To make sure you're not reimporting any infection, place your Data disk in another computer's drive and run full AV scan on the drive. Ditto the Win7 DVD afterwards. We recommend free MS Security Essentials as best lightweight effective AV.

If you have Upgrade version DVD, you'll need to use one of the workarounds given here to install to a clean HD without Vista: Clean Install with a Upgrade Windows 7 Version

The installer is mostly driver-complete, with newer being quickly delivered via optional Windows Updates. Any missing drivers or apps can then be found on the manufacturer's Support Downloads webpage for your model computer, Adobe (flash, Reader) and Java (runtime, free Ofc suite) websites. You might also want to back up your Vista Windows/System32/drivers and driverstore files to browse for any missing drivers, but be sure to scan it for infection along with other data.

Thanks A Lot... I thought I cannot delete or format any of my HD before installing Window 7....