If this is indeed a hardware problem and drivers will not fix it, you need a new card. SLI would not help if the problem lies within the hardware itself since two cards are used as one, therefore, the problem would still exist even though you could use the the DVI output from the new card.
Suggestions for new graphics cards:ASUS EAH5750 FORMULA/2DI/1GD5/A Radeon HD 5750 1GB
- A decent, though lower-end, graphics card for gaming. It will do, but if you have the cash, you may want to consider a better card. $124 (Before $20 mail-in rebate)SAPPHIRE 100283-3L Radeon HD 5770 1GB
- This is a mid-range card that will handle most games well. Whether or not you can play them with all of the eye candy turned on is another matter. $154Palit NE3TS25EFHD02 GeForce GTS 250 E-Green 1GB
- If you want to stay in Nvidia land, this will do too. It is, at its core, a 9800 GTX and is, performance wise, sandwiched between the Radeon 5750 and 5770. $124 (Before $35 mail-in rebate)
Make sure you have the necessary power supply for all of these cards, also, if you are using a slimline or HTPC case, they may require special equipment.