Post [TUT]Complete upgrading guide(root, unroot, flashing ROM & updates)

Here's a tutorial for the new users facing unanswered (at a first glance) questions while browsing through the tremendous amount of information that can be found.
There are many tutorials about this, but I will try to make one unique tutorial that will be easy to understand for everyone.

Press a THANKS button if you think that this TUT has helped you

IMPORTANT!
Before you proceed, you need to understand one thing: although these upgrades work in 99% of the cases, you are doing this at your own risk!
If you have any problems or question with rooting and flashing ROM's DO NOT open new thread, cause I will delete it, post everything here

Before we start, here is little Q&A section, so please READ this before opening new thread!
How to format and partition SD Card?
Read this
Is my desire already rooted?
- Check if you have superuser app in the app list all rooted phones have it
If I root a device which is already rooted, can it mess anything up?
- You can't mess anything up by re-rooting.
Will my phone get the OTA froyo update from HTC here in the US or do I have to do it manually?
- No OTA updates when rooted, to get them you will have to go back to stock to get the update(yepp unroot, or wait for devs to release rooted stock version)
What is S-OFF?
-HTC implemented security on their newer generation phones. This flag, called @secuflag, controls whether your phone has
it's NAND or flash unlocked. Most noticeably, S-ON (security on) will read-lock your /system and /recovery partition, to name a few. Also, secuflag controls whether zip files being flashed through recovery or fastboot, are signed by HTC. The now notorious S-OFF (security off) will disable this NAND security. Since we are unable to access the Radio NVRAM itself (where secuflag is stored), we turned our attention to HBOOT.
Here is How to S-OFF your HTC Desire

If you think I should add more questions and answers, send me a PM



The easiest root method of all is(works for any Desire!):
[GUIDE] One Click How to Root the GSM & CDMA Desire with Unrevoked 3.21



If you want to root using old method, and you have Android 2.2 you will need to downgrade your radio first
[HOWTO] Downgrade Froyo (2.2) to Stock 2.1 (ANY HBOOT | WIN/LINUX/MAC | ROOT)
or
[HOW-TO] downgrade HBOOT 0.92 to 0.80 again
Here is how this thread works:
  • Newbie Friendly How To's w/ Instructional Videos(tnx to dcogen) - post #1
  • Root guide for users who have unbranded(unlocked) Desire - post #2
  • Root guide for users who have branded(locked) Desire and
  • How to make GOLDCARD - post #3
  • Guide how to use fake-flash, unroot, flash ROM and updates - post #4
  • How to remove apps & boot sound, install apps, and many other things - Post #5
    *Unrooting, flashing ROM and updates is same for every device.

There are several methods of rooting device and one of the safest is using Tiny Core Linux(Live CD), since I had several problems using Windows(64-bit) I recommend this option, but if you are using 32-bit OS you should be fine rooting in Windows.

If you have any comments, ideas or requests to improve this thread, post them here
If you find any step that is wrong, or should be improved reoprt it here

Let's start flashing


Newbie Friendly How To's w/ Instructional Videos
Credits
Paul - Rooting method, rooting tool, rooting software, etc
Android dev team - adb, android, etc
craigcrawford1988 - for Tiny Core Linux tut and links
MasDroid - for some tutorials
42turkeys - unroot guide
eViL D: - general help
VeeDubZ - how to remove apps
dcogen - Newbie Friendly How To's
whole XDA community

HTC Touch Diamond -> HTC Desire (AMOLED) -> HTC Sensation -> Nokia Lumia 800 -> HTC One X -> iPhone 5 -> HTC 8X
My ROM's:
Benko's Full & Prime

Benko's Ultra Lite and Clean ROM

Intel Core 2 Quad@3.5GHz | 2x SSD OCZ Vertex | 4GB @1100MHz RAM & ATi 6870 1GB OC'ed