The three beeps is a good sign. It means, your processor must have
been getting power. To make the beep noise, the processor has to
be able to read some BIOS code. No beeps would be worse.
The 2x2 square connector that you connect to the motherboard, should
have two yellow and two black wires. It powers the processor, and
once it was plugged in, you got some beep codes.
Try testing RAM, one stick at a time.
Try the RAM in all the slots (one slot at a time).
It could be, the RAM wasn't full seated. Or the RAM is
the wrong kind, or installed backwards. Verify the RAM
part number, is appropriate for the motherboard model number.
And your processor was probably an i5-650, because I can
find that one on ark.intel.com .
Paul