It's been a while since I rooted my HTC Desire and I should have written about it at the time.
HTC smartphones have a security check so that the ROM can't be written called S-ON.
To have a full root, you need to S-OFF, but for most cases that won't be necessary.
It is possible to have regular root and to use custom ROMs when S-ON, using a custom recovery image. The recovery is a command line shell used to control the ROM.
For HTC Desire and some other HTC smartphones, you can use the simple method of unrevoked:
- unrevoked Home Page
- unrevoked Wiki
Just need to install the drivers for your smartphone, and run the unrevoked tool (don't forget to backup EVERYTHING, because you never know what can go wrong). It will restart your phone and install a ClockworkMod recovery image and root your phone.
After this process you can install any custom ROM and use apps that require root.
I recommend as a first install Titanium Backup for an easy tool to manage your backups of apps and data.
Titanium Backup QR Code: