Go to clockworkmod recovery.
Volume up, power button, and home button all pressed together for a couple of seconds.
Wipe the cache partition
Go to Advanced and wipe the dalvik and batt stats
Go to mounts and storage and select it.
Go to format / system and select it.
Scroll down to format system and select yes.
Go to format / data and select it
Scroll down to format data and select yes.
Go to format / cache and select it.
Scroll down to format cache and select yes.
Now go back and install the rom from the internal or external sd card.