I have a Sony Vaio RS312V which has a Pentium 4 Processor
2.40 GHz but the system seems to work slowly. I have cable
internet service and I have been told that it should be
alot quicker than how it is now. We noticed at initial
start up it says BIOS Update is Incorrect? What doe this
mean and what can be done?

You would be well advised to discuss this with Sony technical support. That is the issue of BIOS warning messages

'Flashing' BIOS to update / modify etc is not something for the inexperienced user

Just like brain surgery: if all goes without any problem, then it's great. However sould you have any problems along the way it is possible that you render your PC completely and utterly useless [by that I mean it won't work at all].