Android phones have a thing called Recovery mode, and stock recoveries just factory reset your phone.
There are many custom recoveries that let you do a hell of a lot more (Including custom ROMs and various other mods and tweaks)
The problem with custom recoveries is that they're very risky and can turn your phone into a paperweight in no time if you're not careful. So i spent about 4-6 hours fucking with LGs KDZ Updater tool with my phone in "Emergency Mode" to get everything back to stock.
But some people never learn, so i already re-rooted it (like jailbreaking except better), put my Amon_RA recovery back on, and got a mostly functional
LG Optimus T (P509), 600mHz CPU, Adreno 200 graphics and 512MB RAM, almost than the computer i had in 2005.
After much dicking around, I got a custom ROM that looks better and works faster and doesn't have all the T-Mobile pre-installed shit you can't delete. Ubuntdroid RC1 (www.ubuntdroid.com) It's based off of android 2.2
The phone has Hardware Acceleration and JIT disabled by the factory for no real reason, since it's completely capable of using them and they improve speeds significantly, so i flashed a zip that enabled them.
The new ROM uses a modified kernel that allows overclocking, I overclocked mine to 729.5mHz, it uses the same vo