I currently have a G33bu motherboard from intel. i plan to buy a graphics card to play games. for future upgrade on motherboard reason, i plan to buy either sli or crossfire enabled GPU and try it first with my current board before i migrate to a board which explicitly says that it support crossfire or sli. does putting either sli or crossfire enabled cards to DG33BU (G33 chipset) will cause any problem? does an sli/crossfire enable cards can work singly on a board does not have dual gpu capabily? please help

It will work. You'll be fine, assuming you have a power supply that can handle the power requirements of whatever GPU you choose.

There will be no problem using a SLI/CrossFire enabled video card with a single PCIE board.

In fact, pretty much all new video cards are enabled for SLI or CrossFire.

Be aware that SLI or CrossFire with anything less than a relatively high-end ($100 or more) video card is not worthwhile. It would be far better to buy a higher end video card than to two lower end video cards.