Are you using the onboard PERC 4e/Si or an add-in PERC 4e/DC?  Which doesn't really matter as they use the same driver - just so I know what we are working with. This is the driver you should be  using ... it is for 2008 R2.  It uses the same basic kernel as Windows 7, so it should be this one you use first.  Keep in mind that R2 is 64-bit only, so if you are trying to install Windows 7 32-bit on this, you may need to check LSI's website for a driver.  They should have an "equivalent" controller under the LSI name since they make controllers for Dell based on controllers of their own.  You might be able to get the equivalent LSI identifier during POST as the RAID controller is loading, or in the RAID BIOS itself.  However, it is unlikely that LSI will have any.  Bottom line ... if the 2008 R2 drivers don't work for you, you may not be able to install Windows 7 on the 1850.      
Hi, trying to install Win 7 on a dell poweredge 1850. Booting from a USB hard drive all goes well until it gets to the hard drive (1 logical drive on LSI raid controller). When I search for a driver all I get is an exe from dell and advice from other forums to use the Win2008 driver. Problem is I can't find the Win 2008 driver. I have 2008 installed on another 1850, but the source files don't seem to be any use as Win 7 says there are no signed drivers for my hardware. Unticked the show only compatible hardware checkbox but still no good. All I'm after is a driver file that Win 7 will recognise. Any help would be much appreciated 
Windows 7 HDD driver