Well, let me begin by saying that this mod is of absolutely no benefit to performance ,however it does affect geek egos. 
Now,many of us overclock our cards to he next “higher” version eg. a 6800 overclocked to say 400/800 is performance-wise no lesser than a 6800GT.So why have the driver remind you that its still 6800?
Solution:Use rivatuner’s device id programmer to make the driver identify ur card as what it should be.
I was pissed off that despite my card (128-bit 5700LE) doing a 425/510 the driver would still recongnize it as an LE.So here goes nothing:
Program ur desired ID string in rivatuner and reboot.U may need to reinstall the driver after this.
PS:This for cards based on same chips like a 6800LE->GT.Its not a good idea to program ur 5200 as a 6600GT though if u feel ur highly overclocked 6600@550/730 should be called a 6600-GT,nothing is stopping u from making it one,virtually! 
Hehe, nice one applies for me actually as my 6800NU is unlocked to 16x6 and overclocked to 375/800, which can be OC’ed more.