Maybe some of you already had this problem and can explain me wtf is going on.

I can't move my mouse from one side of the screen to another without it to freeze for about 2 seconds... At first i thought it was XP's fault (a friend of mine tried to convince me "XP was better than 2000 Pro" - yeah... right) so I formated my C: drive. But even with 2K the problem remains:

My keyboard repeat rate is abnormally slow, Windows beeps when i'm typing "too fast" for him (it reminds me the old MS-DOS beeps), my mouse and keyboard freeze and, sometimes, they stop working at all until a reboot. After the reboot, they may be working or not, it depends. If working, they're always working bad. Sometimes all the keyboard leds blink 3 times and the keyboard dies after it.

I'm afraid the problem is in the motherboard, since both my keyboard and mouse are PS/2.

I'm using Windows 2K + SP3 (in fact i use 2K for more than 1 year and i never had any problems), a PIII 800 in a VIA motherboard.

What do you guys think? I'm sure i'm not infected with some virus or trojan.

Mouse:
If you're using Microsoft's IntelliPoint mouse and have opted to install Microsoft's IntelliPoint mouse software (version 3x and above) that can be the problem, it has caused many people tons of problems - just browse a few popular download sites for an explanation. I found by not installing the IntelliPoint software and just using a generic driver (HID-compliant mouse) that is included with the Win98 CD that all problems have disappeared.

No IntelliPoint here. I have a regular Genius 5€ mouse.

If you have an ASUS mainboard then it's a 'documented bug'. If not, dunno.

First, try different devices. If that works, then you have your culprits right there. If not, then your ports might be tanked.

I've changed my mouse and the problem persists...

Sounds like one, or both, of your ports got cooked. If you have the USB ports available and can get ahold of a USB keyboard and mouse, you might be able to figure out which ports are bad. At this point though it sounds like you'll either have to move to USB or get a new motherboard.