How out of date is my computer? - Windows XP - Pentium III?

- Dell Dimension 4100. I don't know much about this. We have a dial up "high speed" connection on netzero. (I live in Arkansas and am lucky that they just updated our phone service so we can call a larger town (12,000ish) where we could get an ISP.) I am wondering if I need to get Hughes Net or if my computer is too outdated to make a difference. We're trying to start a home based business and have alot we need to do on-line and are having problems getting things downloaded and using audio and video training. Plus things just run so slowly!! We really can't afford to buy a new computer right now!!! Any suggestions? Thank you