Go for a power supply with Active PFC. Power Factor Correction (PFC) allows power distribution to operate at its maximum efficiency. For more information see Active PFC FAQ
i use outlook for its calendar and scheduling. If it didn't have that i would use Thunderbird. I say lets merge Sunbird and Thunderbird together to kill outlook as well as IE!!!
this means you can use your ide hard disk. SATA is way better than IDE (150Mbit/s vs 130Mbit/s) and will only getter better with SATA2. As for the fan connections see if the asus site lets u view the manual for the motherboard, it will tell you.