HOW DO I UPGRADE FROM 2.3 TO 4.4 ON A HTC INSPIRE 4G OR TO ANY OTHER OS?

I just joined this forums-site because I've been looking for an answer for a few days and this site popped up the most.
Anyway here's the issue:
I recently bought an HTC Inspire 4G Unlocked from Amazon. The phone came with an at&t box (since At&t owns that phone in the United States) but the problem is the phone came with Android 2.2 and I wanted to update it to Android Ice Cream Sandwich (4.0). Every time I tap "AT&T Software Update" the "Check for updates" option is grey-ed out and when I...

HOW DO I UPGRADE FROM 2.3 TO 4.4 ON A HTC INSPIRE 4G OR TO ANY OTHER OS?

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