You can try the following resources to find the RC415T-AM motherboard manual:
The RC415T-AM is a socket 775 motherboard, supporting Intel Core 2 Duo, Core 2 Quad, and Pentium D processors. It features: rc415t-am motherboard manual
Plugging the Power LED into the HDD LED pins – the manual color-codes this clearly. You can try the following resources to find
This is the #1 reason people search for the manual. The RC415T-AM uses a compared to modern Intel boards. Here is the official layout (viewed from top, with the missing pin at the top right): supporting Intel Core 2 Duo