Random text crashes?

[Whiplash]

Over the past month my comp has crashed randomly while viewing text files. not every text file and not within a time frame, sometimes i can view text files for hours and others just minutes. today i crashed on ebay. so the problem happens on msword, notepad, firefox, IE, wordpad, Thunderbird(email) etc.
i get no error messages just a screen freeze with parallel vertical black lines approx. one inch apart. when this happens i can't do anything, ctrl+alt+del does nothing. i have to power off by holding the power button.

i have added nothing new to the mix and i have ran Spybot, Adaware and norton finding nothing. Could it just be old age?

Specs (don't laugh):
Windows 98 SE
4.10.2222 A

Intel P3 500Mhz
512Mb SDR pc100 RAM
Gateway(?) 13Gig HD Master
Maxtor 40 Gig HD Slave
Voodoo3 4.12.01.0666 3/7/2001
Creative Soundblaster Live! Value 4.11.01.0711 10/7/99
US Robotix 56k Internal 1.60.009 10/12/2002
Realtek RTL8029(AS) PCI ethernet NIC 4.29.98.0514 4/23/1999

six months ago i replaced the power supply, seems to run hotter. also this comp has never had a fan other than the one attached to the power supply.
I don't know if heat is the issue, i would think if it was i would have noted this happening right after installing the new supply.
any way to monitor the heat? ( i know there must be)

thanks in advance for any help the wonderful people of the tech forum can offer.

 

[liggyman]

try adding a case fan to blow across the voodoo3 heatsink. those cards only have passive cooling and still run really hot.

The distorted display when the lockup occurs makes me think video card.