I just instilled some new memory a 2gb Matched pair of XMS2 5400-C4, the timings are rated at 4-4-4-12.

Even though the memory is rated at those timings the SPD is set at 5-5-5-15. No problem I thought ill change them in the BIOS but when I started to change them I noticed another setting "Row to Row Delay"tRRD, I have no idea what I should set this at as I've not seen any information for it on the corsair web site.

Its set on AUTO atm as I'm not sure what it should be set at, any ideas or just leave it on AUTO.

I have it set to 2t for my DDR1 RAM, but for DDR2 youd be looking at a higher figure.  Set to auto and leave it so if your PC is stable.