Ok ...
Try the latest driver from Intel (since Dell does not support Windows 7 or 8 (and no Server OS's), the Vista driver is the latest Dell offers, and may not be sufficient):
Intel Rapid Storage Technology (use the "f6flpy-x64.zip" version - or even try the "iata_enu.exe", but it should not be necessary)
If that doesn't work, boot to the BIOS Setup (F2), SATA Operation, change to Autodetec/ATA or Combination ... this way is not ideal, but will probably work.