Heres my sypmtoms:
-Sometimes on booting, either hard drive isnt found by BIOS
-On occasions, attmpeting to read a DVD or CD results in drive cutting out, and PC freezing, with the optical drive door refusing to open
-Wireless connection disconnects when PC is under load
-Hard disk 1 or hard disk 2 (both 200GB) may simply stop during normal computer use, resulting in Windows crashing (if HD1), or half of my programs stopping (if HD2)
And the biggest of all:
The PSU size calculator reccomends a 451W power supply. I am running a 400W "Hyena" branded one.
Am I wrong to say it is indeed the power supply?
There are only 3 common factors in all of these things:
1. The PSU
2. The motherboard (still less than 1 year old, and under warranty)
3. The hard drives, both under 1 year old, and under warranty
Also, what would be a good power supply to get. I want atleast a 500W for now, just to restore reliable pc use. I also want to keep the price under $100 NZD ($75$ USD) (40 Pound)


Highly recomended. 

'nuff said