I don't think IP addresses change automatically. But there is a way to check.
See my little penguin in my sig? He tells you your IP address (among other things). Check my sig every once in a while to see if it has changed. If it has, make a new VMK account and try to get on.
If your IP doesn't change itself...
...
Don't go buy that computer!! It's a total waste of money. Especailly when you can just take the power wire out of the internet box (cable, DSL, or broadband only) and keep it out for 5 minutes. If that fails, unplug it for 8 hours (overnight works best).
If that fails, do this (this is the only one that will work with dial-up):
Click Start-->Programs-->Accessories-->Command prompt
Type "ipconfig /release" (without the quotes)
Type "ipconfig /renew" (again, no quotes)
If all that fails, do this exactly as it is written (this won't work with dial-up):
Click Start -->Programs-->Accessories-->Command Prompt
Type "ipconfig /release" (without the quotes)
Shut down your computer
Turn off your computer
Turn off all ethernet hubs/switches.
Turn off cable/DSL modem.
Leave off overnight.
Turn everything back on.
Lastly, don't try to get the easy way out and get an IP changer utility. They don't actually work.