That appears to be a P4 or PIII machine, which I believe pre-dates the alienware brand Nope, Alienware has been around since 1996.

Edit: PIII by no P4 power connector.
P4 because large wire bundle appears to have at least 2 12 volt lines (yellow), but the 20 pin ATX connector has only 1. I checked: The proprietary Dell connector also had only 1 12V wire