2.3 Gingerbread trouble on the Desire HD

[Mr HD]

Hello , im new to this forum so sorry for any silly / stupid things i may ask.

Right im getting trouble installing, 2.3 Gingerbread onto my Desire HD i get as far as on the progress bar it says signiture , and then tells me that, its unable to install 2.3 because of the ROM or something alone them lines.
Anyone got any good ideas how to solve this ?

Thanks