Hey Sk,
YES YOU CAN!
What You'll Need:
• An HTC Touch Diamond or Touch Pro (GSM only. Folks with CDMA handsets—that's you, Sprint and Verizon—go here or here.)
• A (free) account at XDA Developers
• A Windows Mobile 6.5 ROM (Lotsa choices here: Diamond, Pro)
• A Windows PC, set up to sync...