errrr....
Damn... this one hurts my head...
So before going and hurting your own anymore I would say do this:
(My opinion here: Opjose may have much better suggestions)
Double check your install job on the new hard drive and you are 100% certain nothing is wrong then
1) Put your original hard drive back in the box and make sure you can still boot orginals, etc...
2) If it still has the same symptoms then you know its not the new hard drive.
3) If it behaves normally again then you know its the harddrive.
2) Cont. If it exhibits the same behavior with the original hardrive then the problem is some where in the xbox hardware.
Since you know it was working before the modchip, right?, then the next step is to take a closer look at the modchip install. Wiring and Bios used.
3) Cont. If it behaves normally again then something went wrong with the new hard drive install.
Instead of repreping the whole drive again
(which is what you really should do)
You might be able to get away with:
Formating all 6 partitions with FlashFXP,
complete a re-copy of original OS to the xbox C partition via FlashFXP.
Make sure you can boot originals and backups before installing Evox.
Install Evox if everything still looks good...