Bill: First, welcome to BC where the experts (and I'm not one of them) can fix anything. But before this can happen, much more information will be needed about your hardware (make, model, amount of RAM, etc.) and which operating system you use (i.e. is it W98SE?). It would also be helpful to know about what (if any) protection you have such as anti-virus, firewalls, etc. (and BTW, you can learn much about protective software by studying the BC Tutorials). And lastly, describe what you might have been doing just before the problem erupted, i.e. did you add any new software or hardware, do any tweaking, etc. More info is better than less.
Post back with more info; I'm gonna step aside and let the pros help you from now on. Good Luck!