Color us confused on this one, but there's controversy broiling over exactly how much RAM the original HTC HD2 has. Coming on the heels of HTC USA's revelation that the T-Mobile US version of the HD2 will have 576MB of RAM compared to the European model's 448MB, the suggestion is that HTC purposefully hid 128MB of RAM on the initial model. That's compounded by a purported leaked ROM from T-Mobile's handset, which some users have reported "unlocks" the hidden memory.
In the process one HD2 owner has dismantled his smartphone to check the parts inside, and others have been thinking up more imaginative ways to test the memory. For instance, XDA-developers' Brandi attempted to use up as much of the RAM as possible with running apps, and reports that he was able to use more - 444MB - after installing the leaked ROM than prior to that.
It's unclear why HTC would purposefully undermine the original HD2 in such a manner, and you can bet we'll be asking them about it (and probably getting a "no comment" reply back, frustratingly). Until then, this puts the whole Windows Mobile 7 upgrade question on a completely different footing.