Rooted the phone and installed cyanogenmod. How to get back Sense UI? I have a HTC Desire comes with Sense UI when bought. I rooted it and installed Cyanogenmod. Is there anyway I can get back my Sense UI. I don't mind removing Cyanogenmod.
You're going to need to install a Sense-based ROM. CyanogenMod is basically a customized build of the Android Open Source Project (AOSP) code, which is released in source form by Google. They use only open source components, and Sense is a proprietary, closed source UI made by HTC.

Installing a ROM with Sense is very easy, though. The procedure will be just like flashing CM - boot into recovery and flash a .zip file with the ROM that you want (alternatively, install via ROM Manager, whatever you prefer).

There are custom Sense ROMs as well as "stock" rooted ROMs floating around. The XDA boards have a handful of each. You can find a rooted stock ROM here, though, if you're looking to go back to the original system as provided by HTC (but retaining root).

Edit: I answered this under the assumption that you have no backups to work with, but if you used ClockworkMod to create a backup of your system before installing CM7 (which is highly advised for any future readers out there!), you can restore that backup and...well, be back where you were on a stock rooted system. After all, that's the point of the backup!