Computer help: Power supply not up to the task

Power supply not up to the task

I have a Sony Vaio Desktop. 512MB RAM, running Windows XP SP2.

It has two optical (DVD) drives, and two hard drives. It also has a double-headed video card, and a USB/Firewire PCI card. All of those things take power (the Video card and USB/Firewire cards have taps into the main power supply).

I am trying to add a Belkin KVM switch so I can use my primary keyboard/mouse and monitor on both my home (the Vaio) and my work pc.

When I connect the PS/2 keyboard, mouse and monitor up to the KVM, and then turn the computer on - the PC starts up, gets past the initial BIOS check, but then reboots - before Windows really has a chance to get started. It isn't just a single reboot - it keeps rebooting over and over again - at the same point. Keyboard doesn't even work to select SAFE MODE.

[Before the KVM install - this computer will run for days, weeks maybe even months before it needs to be restarted]

What I think the issue is - is that this Belkin KVM doesn't have its own power supply (it can be bought separately as an accessory). It is parasitic off of the host computer via the PS/2 or USB port. I think when the KVM goes to suck power at start-up - it puts the machine over the edge - and causes the reboot. Over and over again.

[Already posted something to Belkin, but they are business hrs support only for KVM's]

Is this (sudden reboot) the normal symptom when the power supply is overtaxed?

Thanks in advance for any pointers or suggestions.

Robert