There are several things that could cause this from a hardware problem to a simple stack error. Try the following and see if it fixes it:
1. Edit your config.sys file so that it reads:
STACKS=64,512 ;(this is the maximum allowed)
FILES=60
BUFFERS=40
Save it and reboot.
That usually fixes it. If not, you need to look at what happened just before you received the error. Did you install a new program? A new piece of hardware? In short, these error messages don't just appear without a reason. Something changed and in order to troubleshoot, we'd have to know what changed on your system. Some known incompatibilities are trident video display adapters and certain display drivers. Did you update drivers recently? Hope this helps,if not, respond with more info!