Do I need to delete all partitions when doing Clean Reinstall ?

I am reading posts here but when you tell them to do a Clean Reinstall why do we need to delete all partitions ?
Is it okay to only delete the partition where windows will be reinstalled ?

Deleting the partitions is not required at all when reinstalling, Windows will install itself in any already created partition you can have or you may chose to delete and recreate, but it's your choice really.
It's neither mandatory to format them. Not even the one you're installed on if it's already created, all the data there will be still there after the install.

Lovus said:

I am reading posts here but when you tell them to do a Clean Reinstall why do we need to delete all partitions ?
Is it okay to only delete the partition where windows will be reinstalled ?

Yes, it is OK to delete just the OS partition, but not necessary. However, when it comes to computers, I always go with the possibility that something may go wrong; therefore, I backup the data on the partition I am preserving as a safety net. Worst case scenario, I won't need it.

There is a good article on the process at the following link;

http://pcsupport.about.com/od/operat...all-part-1.htm

HTH

Thanks for opinions. Now I have an idea what to do when doing Clean Reinstall

To do a CLEAN REINSTALL is Just that. A CLEAN REINSTALL. Without Deleting all partitions you really are not doing a Real Clean Reinstall.

Now it is up to you what you want to do.

If you have the typical Win7 HD setup it will have a 100-200mb System Reserved partition which boots Win7, followed by the C partition housing the OS. Then it may also have a data, Recovery and tools partition.

If you reinstall only to C and ignore the other partitions, it will place the System boot files on C abandoning the System Reserved partition for booting Win7 and making it wasted space. The only way to avoid this is to delete both System Reserved and C during install so that the installer handles this correctly.

Now as to any other partitions like Data, Recovery or OEM Tools which comes on many factory preinstalled Win7 machines. Data is up to you although saving your data there during reinstall is not a responsible backup method. Recovery and OEM Tools (bootable diagnostics) may or may not run afterwards so we recommend making your Recovery disks before reinstall.

This is further explained with more details on the various OEM partitions viability after reinstall in Clean Reinstall - Factory OEM Windows 7. Many users don't even want Factory Recovery which contains the preinstalled crap that throttles and corrupts Win7, so deleting those partitions is fine with them after perhaps making their Recovery disks as a backup in case a new owner might want them in the future.

Looks fine, get rid of the pirated windows 8 garbage.

Pirating is not tolerated here.