Late last month the hardware world discovered a way to overclock ATI Radeon X800 Pro graphics cards to a Radeon X800 XT Platinum equivalent (news), by means of flashing the card BIOS and re-enabling 4 pixel pipelines on the R420 GPU that are disabled by default on X800 Pro cards.  That covers the basics, but since then more detailed instructions have surfaced like this guide posted on the PCUnleash discussion boards, translated from a Korean article found here.

One important tidbit of information the guide reveals is that so far only R420 GPUs with featuring a serial code that ends in a "1" (one) can be successfully modded in the above manner.  In other words, R420 GPUs with serial codes along the lines of "GAXXXX.1" (X can be any other number here in this case) are the safest bets for modding.  The only exceptions so far appear to be the GPUs with "8988.1" and "8808.1" serial codes, but it might be a little early to leave it at that.  Nothing is quite set in stone yet, but the guide does note that they haven't had success with R420 GPUs branded with any other type of serial code.

The guide also notes that modding the X800 Pro into an X800 XT also allows the user to make use of ATI's "Overdrive" overclocking utility (available on ATI's recent Catalyst graphics card drivers) that the X800 Pro normally cannot support by default.  Use of a modified driver may be required to get the utility working, however.

Of course, that still doesn't make the actual hard-mod itself (which naturally voids your card's warranty) any easier, so don't try this at home if you're not confident with your hardware!