Hi everyone!

I'm currently working on recreating a 1998 PC that I used to own. The mobo is a Chaintech 6btm, equipped with a Pentium II 400 and an Asus V3400 (Riva TNT). I've connected it to a modern Philips 27" using a VGA to HDMI adapter, powered by USB.
However, I'm encountering an issue. When I attempt to power on the system with all the mentioned devices connected, I hear a continuous high/low tone beep code (similar to a siren) and there's no display on the monitor. On the other hand, if I disconnect the VGA card, I get one long beep followed by three short beeps.
The power supply unit (PSU) I'm using is a Delta 350W. I also tried a modern Chieftech A80 with the same result.

I'd appreciate an assistance in pinpointing the faulty device - whether it's the CPU or the VGA.

Thanks!