SLI set up problems, graphics card issues

Hi folks hope you guys can give me some advice on some issues that i have been having.
My old off the shelf HP system finally died and give up the ghost so i decided to see if i could build my own cheap gaming system with some bits from the old system and other bits i could pick up cheap on ebay and computer fairs and the like.
To be honest i have tinkered with builds before so i would say i a not a total novice but as with everything knowledge is stretched when you encounter problems.

Here is my system spec that works fine.

Intel core 2 quad q9550 2.8ghz with (Artic cooling freezer 7 pro heatsink)
8GB Corsair Domminator ram
EVGA nForce 780I sli ftw motherboard
Nvidia GTx 260 Gainward graphics card
Corsair HX620w PSU
Windows 7 64bit clean install and updated

Nvidia drivers updated and loaded and working fine. Computer runs fine no issues.

Getting brave i decided i wanted to try and SLi the system. Here is where i started to run into problems. I done my research took advice and took the plunge and purchased a GTx 260 inno3d freezer x2 card very cheaply which i beleived with what i could find out should work with my existing card with no problems.

Because of the layout of the motherboard and the phyical dimensions of the cards and the fact that i have a 1gblan card fitted in the pci slot i have to fit the gainward in PCIe 3 and the inno 3d in the pcIe 1 and then fitted the SLI bridge and power leads and booted the pc.

Computer does not get past post does the usual bios startup memory test etc then stop displaying message.

"Non sli card detected in pci_2 or 3 please move to pci_1 for non SLi operation". Now i am thinking that i have not installed the new card correctly, bridge not fitted correctly or the new cards is faulty (like i said got it cheap). I checked everything found everything as it should be installation wise.

I removed new card put everything back as before computer boots fine.

Next thing i tried was boot the system with the new card i get one beep then a black screen then nothing, everything seems installed correctly and card has power. So ok pays your money takes your chance a duff card me thinks.
I had friend who installed the card and he got it to boot and run but after a while it froze his system (possibly a driver or heat issue but the card did work, he only ran it as a single card not sli).

Got card back reinstalled and got same results as before. Dual card results and single card results with new card.
Gainward one stills boots fine as single and computer runs fine. Difference now is that when the computer boots on post bios displays "SLi memory detected but disabled" when i have just the gainward one in.

Looked through motherboard manual found about fsb & memory config menu in bios (lack of knowledge here thought motherboard would autodetect and set accordingly)Anyhow enabled it tried various settings still no difference altough bios did change to say enabled to whatever setting i set in the bios but results where the same as before with cards.

Have tried my old GTX 9800 graphics card in pci_2 and the gainward in slot with the sli bridge and the coputer booted fine detected the 9800 and loaded drivers so ended up with to nvidia control panels but not able to to set sli which as i expected as the cards are different.

I managed to get hold of another inno 3d gtx 260 freezer 2 and get exactly the same results so am guessing that its a motherboard issue.

I apoligize for length and verbose content but thought i would try and supply as much info as i can.

Many thanks in advance for any ideas or thoughts.