I went awat on holiday for 1 week. I shut my PC down but did not turn off the mains supply. On my return I tried to boot up my machine but all I got was a 2 tone noise from the system speaker and no display. I then searched the internet for answers. It was suggested on some forums that the PSU had probably malfunctioned and replacement would be a good idea. On inspection inside the case I also noted that the fan was clogged with dust and after cleaning made a horrible noise. Next I purchased a new 400w PSU a new heatsink and fan and Whilst in the process I have doubled the RAM. All of this came to no avail so again from a suggestion I removed the battery to clear the CMOS and enable the BIOS to default to factory setting. After all of this I still have the original problem. Sometimes when I power up, no noise is heard from the system speaker and on others the siren sound is there. If I could get some sort of display I could check other settings but there is no video output at all. The CPU fan is spinning alright and the LED on the motherboard is lit. A brief summary of my hardware is as follows. Asus A7N-266VM Motherboard with onboard everything (except the modem) AMD XP 2000 CPU 2x256MB of RAM, 400W PSU, 40GB Maxtor Hard Drive, Toshiba DVD ROM, Liteon CD Writer, 1.44MB Floppy Disk Drive, Opertaing System Windows XP Pro. I have now spent 1.5 days trying to resolve this problem, any help would be gratefully received. Thanks