How can I calculate power consumption of my PC in Watt, to prove my House owner ( I live on rent) , my PC doesn't consume much power? He blames me for Huge power bills even he too use Fridge, A.C. etc and his son watch the TV all the time.

We both share one Power meter so for bill we pay 50%-50% but He is saying I use PC all the time even night i keep on for downloading.

I just want to calculate power consumption of my PC then will calculate monthly expense of unit as per my City's per unit price for power.

I've

Windows: Microsoft Windows XP Professional 5.1.2600 Service Pack 3
Memory (RAM): 960 MB
CPU Info: AMD Sempron(tm) Processor 2500+
CPU Speed: 1399.0 MHz
Sound card: Vinyl AC'97 Audio (WAVE)
Display Adapters: VIA/S3G UniChrome Pro IGP | NetMeeting driver | RDPDD Chained DD
Monitors: 1 - 17inch LCD - LG
Screen Resolution: 1280 X 768 - 32 bit
Network: Network Present
Network Adapters: Bluetooth Device (Personal Area Network) #2 | WAN (PPP/SLIP) Interface
CD / DVD Drives: I: ELBY    CLONEDRIVE
COM Ports: COM1 | COM2 | COM7 | COM8 | COM9 | COM10
LPT Ports: LPT1
Mouse: 3 Button Wheel Mouse Present
Hard Disks: C:  29.3GB | D:  29.3GB | E:  97.7GB | F:  97.7GB | G:  211.9GB
USB Controllers: 5 host controllers.
Firewire (1394): 1 host controllers.
Manufacturer: Phoenix Technologies, LTD
Product Make: MS-7142
AC Power Status: OnLine
BIOS Info: AT/AT COMPATIBLE | 01/18/06 | VIAK8M - 42302e31
Motherboard: MICRO-STAR INTERNATIONAL CO., LTD MS-7142
Modem: ZTE USB Modem FFFE CDMA #2