Insert Windows 7 DVD, set CD-ROM as 1st boot device in BIOS, press any key to start setup when asked, click 'Install now', click 'Custom (advanced)', click 'Drive options (advanced)', click on your current Windows partition and delete it and once again click the 'System reserved' partition and delete it. Now click on the unallocated space you gained from deleting your old Windows and system (boot manager) partitions, click new and confirm (Windows will automatically recreate system partition for new boot manager).
If you already have windows 7 got to Control Panel->System and Security->Administrative Tools->Comp. Menagment->Disk...
Right click on partition you want to format and click 'format'.
Note!!! You can't format current partition.
If you want to do a clean install then just launch system installer from a floppy or usb and you'll get HDD/SSD options.