in my Dell Desktop optiplex 990 two lights are on i mean the 1 and 3 which i am unable to install the windows what is the problem can any one help me.
actually i have purchased newly this computer.
According to your service manual found here ftp://ftp.dell.com/Manuals/all-products/esuprt_desktop/...
on page 78, it means that there is an issue with the ram and has the following troubleshooting advice
"Ensure that no special requirements for memory module/connector placement exist.–
Ensure that the memory you are using is supported by your computer."
I might suggest ensuring the ram is fully seated in it's slot(s)