HP PC does not start properly

Hello

Already more than 4 months that I am Unable to start or restart my pc I am obliged each time to turn it off, cut food, open, remove the battery from the motherboard and put it after a few seconds, replace the food (the computer immediately goes on), I turn off by the "power-on" front, and I turn for everything to work. The BIOS launches, I have two very brief beep (it has always been this way) and I have to adjust the time because I see the clock midnight to 1 January 2002. I tested the memory cards one after another, this happens.

My configuration:

Motherboard MSI MS-7225 ver 1.2 rohs
Processor Type: AMD Athlon 64 X2 5000 +, 64-bit Technology
2 DDR II SDRAM 512 MB each
Hard drive: 1 x 250 GB - standard - Serial ATA-150 - 7200 rpm
PCI Express x16 - plug-in card
GPU: NVIDIA GeForce 7500 LE TurboCache supporting 512MB
Type: Sound card - Integrated

I have exactly the same pb, except that I have great disconnect, remove the battery, reconnect, restart, it does not tjs (mm config my motherboard with a 7225 version 1.0 and then I tried with a 1.2 cm in 7225 the worm pb is always the same).

I forgot to specify that when I start my PC without preconditions, all the fan running even when the lead front is lit as an indicator of hard drive activity. But never did the BIOS is active.