RAM problems

I now have the solution to my problem and will never buy Corsair Ram again.
Just to walk you through the story, if anyone is interested:

1. A 4GB stick went faulty and was returned to Corsair's Netherlands facility.
2. Netherlands received it and ordered despatch of a new 4GB stick from Taiwan. That stick turned out to be high-density, single rank.
3. I returned that to NL and had to also give them a perfectly good stick of dual-rank ram as they claimed the dual-rank was now only available as an 8GB pair.
4. They sent 2 sticks of single rank ram
5. I queried and they said it was a "picking error"
6. I had to return them to NL.
7. They sent another 2 sticks of single-rank. I queried and they said it was a "production error"
8. I returned it to NL
9. They finally sent the correct 8GB of dual rank dimms.

In fairness, it only cost me £12 to send the first stick back to Netherlands. Every other collection and delivery was done by UPS and paid for by Corsair. I suppose they have a massive transport contract.

In summary then. I reckon Corsair has very poor QC procedures but very good customer service back-up.
Next time I'll use Kingston or Crucial.
It took 6 weeks to resolve with Corsair and I really don't want to go through this again.

dell OptiPlex 780 dt , my dell uses dual ranked ram as opposed to single rank , I had the same issues when I tried to use the singke rank , no boot , no screen , machine fan would start , audio codes emitted , plus light flashing codes , memory codes !

single rank is faster and more exspensive , its faster because it makes one loop , where dual rank makes two loops