After a little confusion earlier this month, it was eventually revealed that HTC wouldn't be updating the venerable Desire HD to Android 4.0 Ice Cream Sandwich after all. At the time, the manufacturer simply said that the current Gingerbread-based firmware "provides customers with the best experience" on the phone. Now HTC has elaborated a little on the specific technical issues keeping the DHD from getting an Android 4.0 update. Basically, the system partition of the phone isn't large enough to hold Sense and Ice Cream Sandwich, and HTC found the device's performance on ICS to be below-par anyway.

Here's the company's statement in full, which goes into a fair amount of detail about what's involved --

We’ve heard your feedback on our decision not to update the HTC Desire HD to Android 4.0. We completely understand that this is a controversial decision. For more background, due to how storage on the HTC Desire HD is partitioned – and the larger size of Android 4.0 – it would require re-partitioning device storage and overwriting user data in order to install this update. While technically advanced users might find this solution acceptable, the majority of customers would not. We also considered ways to reduce the overall size of the software package, but this would impact features and functionality that customers are currently using. Even after installing the update, there were other technical limitations which we felt negatively impacted the user experience. We believe an update should always improve the user experience and carefully evaluate each update based on this criteria. While we are very aware of the disappointment from this decision, we believe the impact to user experience was too great. We recognize this is a change from our previous statement and for that we’re truly sorry.

So that's that. Clearly there's no way HTC could have anticipated the hardware or partitioning requirements of ICS when designing the Desire HD in mid-2010, so it's the decision to cut the update is an understandable one. Nevertheless, we're sure custom ROM developers will still find a way to get ICS ROMs loaded onto the Desire HD's smaller partition setup. So if you're still rocking a DHD, the custom ROM route should still be open to you.

Source: HTC Blog