HTC Desire low on internal storage, I'm clueless -- Any help? It's been bugging me for a while but getting quite bad lately. I get warnings that my internal storage is full, I have about 13mb left of what I believe is 512mb worth of rom. I have checked with the app "diskusage" and my apps take about 122mb, with about 20 more mb being used by "data" (unsure what this is). When I check the apps list, my biggest app is some 12mb, and even within the first screen of apps this drops to just over 6mb. So I don't have extremely big apps, and I don't have all that much of them either. I try to put most on my sdcard, so no problem there either.

How do I figure out what's hogging all this space, and how do I fix it ?

On a related note, what is the Android equivalent of "formatting" your phone? I believe factory settings doesn't remove all data (sdcard etc) or does it?

EDIT: I have done a hard reset on my phone, and the free space available is somewhat similar to what I saw before. So, is it normal to only have about 150mb available for apps when the internal rom should be 512mb ?
One problem I've noticed is the (at least in Android Froyo), the stock Web browser caches to the phone storage. The browser cache can quickly take up 20+ MB and therefore use up free internal storage. 

I've moved to using an alternate browser (Dolphin) and set it to cache to the SD card. This has removed my "low internal storage" limits; my free internal storage space now stays much more consistent except when installing new applications.