Okay, I came here to find a way to do this and found it (in seven different threads + a few outside links), so for anyone else, here it is in one place.
1.- Download this file
, it has everything you need. Extract it somewhere.
2.- Most 9000B's seem to have the 3-button options locked, so first we need to unlock that.
2.a.- Enable USB debugging on your phone.
2.b.- Open up Odin3 (in Vista and 7, "run as administrator...").
2.c.- Connect your phone to your PC.
2.d.- In Odin3, under "PDA", find "Aries_P-SBL.tar.md5".
2.e.- In Odin3, make sure "Re-Partition" is NOT selected and "Phone Bootloader Update" IS selected.
2.f.- In the boxes at the top, check that your phone is connected.
2.g.- Click "Start", it should take 40 - 50 seconds to do the update.
2.h.- After reboot, turn off your phone and try [VOLDOWN+HOME+POWER] to see if it worked. If it did, you´ll get the digging android logo, on to the next step.
3.- Now we need to root the phone. The one-click-root we´ll be using is modified to work with the i9000B.
3.a.- Disconnect your phone and shut down Odin (if it is open).
3.b.- Enable USB debugging on your phone.
3.c.- Connect your phone to you PC.
3.d.- Open "Galaxy S I9000 One-Click Root.exe" (in Vista and 7, "run as administrator...").
3.e.- Click "One-Click root 2.1".
3.f.- After the reboot, the phone will be rooted.
4.- Now we flash Froyo onto the phone.
4.a.- Take out your SIM and SD cards (MAKE SURE YOUR BATTERY IS FULLY CHARGED BEFORE GOING ON).
4.b.- Hit [VOLDOWN+HOME+POWER] to go into download mode (the digging android).
4.c.- Open up Odin3 (in Vista and 7, "run as administrator...").
4.d.- Connect your phone to your PC.
4.e.- In "PDA" find "JPD_JPD_JPD.tar"
4.f.- Click "Start", it should take around 2 minutes to flash your phone. DO NOT DISCONNECT, TOUCH OR EVEN LOOK AT YOUR PHONE UNTIL ODIN SAYS "FINISHED".
4.g.- The phone will reboot one last time and instead of your operator's startup screen, you'll get the standard glowing S. It will stay on that screen aproximately 1 to 5 minutes (depending on the amount of data on your phone), once it is done it'll go to your home screen.
4.h.- Your home screen will be reset to factory, but all your apps & contacts will still be on the phone.
5.- Now to enable paid access to the market.
5.a.- Enable USB debugging on your phone.
5.b.- Connect your phone to your computer.
5.c.- Open "SuperOneClick.exe" (in Vista and 7, "run as administrator...").
5.d.- Click "Root".
5.e.- After 50 - 70 seconds, your phone will reboot and it will be rooted.
5.f.- Go to the Market and install "BusyBox" (only from the market, you don't need to open it and do the final install, we just need two different mods that BusyBox puts on your phone.
5.g.- Go to the Market and install "MarketEnabler".
5.h.- In MarketEnabler, FIRST BACKUP YOUR CURRENT SETTINGS (and I'd recommend writing down your opcode just in case).
5.i.- In the second screen, long-press on one of the operators listed and click "fake this provider now".
5.j.- If your Market is open when you fake the provider, you need to kill it and restart it since it checks on startup.
5.k.- To go back to your standard market, click "Restore settings" in MarketEnable and presto!
Well, that's how I was able to do it. I flashed three Movistar Peru phones and two Claro Peru phones, all five are working fine, MobileTV works and the system is faster, no bricks or errors. This is not a guarantee, just the way I did it and it worked for me, if you brick your phone there's nothing I can do about it.
Hope this helps someone.