For a long time I have been wanting to root my HTC Aria and get a new ROM. Here are some of things I wanted:

• Ability to tether or make my phone a hot spot w/out paying tons of money to AT&T to use the data I already pay for (jerks)
• Ability to install apps not in the app store, such as Amazon's new app store.
• Ability to see the latest and greatest Android software just for fun.

I have been too timid to risk turning my phone into a brick, but recently my HTC Aria had an unfortunate accident. Since my phone's already kind of jacked, I am now less protective of it and decided to give rooting a try.

What does it mean to root a phone and put a new ROM on it?

For those of you that are interested in getting the latest Android software on your phone, but don't really understand how it works, I'll explain it as simply as I can. The Android operating system is open source. That means it's free and you can get updates to it all the time. The problem is that companies like AT&T like to customize the software a bit for branding purposes, to try and be better than the next company and also, to disable awesome stuff like tethering so they can charge you a ton of extra money to re-enable it. Not only is this cool stuff disabled, but when updated versions of Android become available, you have to wait for AT&T to do their stuff to the new version before it is available to you. This takes a loooong time.

You could get around this by simply installing the latest Android software on your phone, therefore completely wiping what the carrier put on there. Carriers don't want you to be able to do this, so they take some measures to prevent you from being able to do it. Basically, in order to reinstall the software on your phone, you need to get administrative access to your phone. The Android operating system is based on the Linux. On Linux, the main administrative user is called "root" so that's why people say they want to "root" their phone. They are getting access as that user. Once they have that access, then they can have full control over their phone to reinstall the operating system or whatever else interests them.

Getting root access to your phone is the most tricky step because there is no dependable way to do it. Basically someone has to find a security vulnerability for you phone. Then they package that vulnerability up for you so you can easily run a little program to do the hack for you. Security vulnerabilities change from phone to phone, so there are many hacks out there and you have to find one that works for your phone. For my HTC Aria, unrevoked3 is the only one I'm aware of that works.

Once you have root access to your phone, there are two remaining steps to get a new operating system on your phone. First, your phone has a recovery mode that you can boot into in case your phone is jacked up and needs to be fixed. You will overwrite this recovery software with one called ClockworkMod. Once you have that installed, you just download a new ROM (basically a copy of Android OS), put it on your SD card, boot into your new ClockworkMod recovery and install the ROM from there.

How to actually do it all

Doing all this stuff is already well documented. I'll just point you to the docs I found most helpful and I'll point out stuff that I had trouble with.

• There is a cyanogenmod wiki page that explains everything for HTC Aria. Start there.
• You can run this stuff on Windows, but I had tons of trouble with it. I ended up downloading the Ubuntu Live CD and running it all from there. Things worked great once I did that. If you insist on doing it in Windows, be sure to install the HBOOT driver and make sure HTC Sync is installed, but not running. In most places it says to uninstall HTC Sync, but you actually have to have it installed because there are a few libraries it provides that are needed. So install it, but make sure it's not running. Again, you don't need to worry about any of this if you just use Linux.
• I used RomManager (an app in the App Store) in install ClockworkMod. The instructions tell you that you can also use RomManager to download and install a new ROM. I had lots of problems with this and never got it to work. What I ended up doing was option B which is to just download the ROM directly from cyanogenmod.com, copying the ROM to my SD card, booting into ClockworkMod recovery and then installing the ROM directly from there.
• For some reason, it is not documented practically anywhere, but when you plug your phone in over USB to run unrevoked3, your USB mode must be set to charge only.
• When I try to boot into ClockworkMod recovery, for some reason I just get a little picture of the Android bot with an exclamation over his head. Useless. What I finally found is that when I see that, I need to take my battery out quick and put it back in. Then it will boot into ClockworkMod recovery successfully.

Good luck with your own rooting adventures! If you have questions, post them as a comment and I'll try to respond quickly.