How to save contacts in iPhone so it can be used for transferring it to my HTC Desire?
I am assuming that you sync your iPhone to iTunes on either Windows or Mac, and that these  contacts are then displayable in Apple Address Book or an equivalent program on Windows (Microsoft Outlook, etc.).

The procedure would be to sync all your contacts from the iPhone to the Mac or Windows program, then use that program to export the contacts in a database format that could then be imported into the HTC Desire software, or the software on Mac or Windows that you use to sync data with your HTC Desire.

Update:

Since you have indicated that you are using the iPhone to sync to iTunes on Windows, then this forum may not be the best place to ask this question. You will need to use programs that run on Windows to get the contact data reformatted into a format suitable for importing into the HTC Desire, and you will need to use Windows software to upload it into the HTC Desire as well.

People on this forum tend not to use Windows for these kinds of functions, so I suggest that you also post this question on a Windows-centric and Android-centric smart-phone support forum.