"Failed to obtain a trial serial number"

My old PC broke so I bought a new one, and I had to download and install RPGMXP again. However, any time I try to run RPG Maker, I get this error message:

What can I do to resolve this? Could the reason for this error be that I'm using Windows Vista? And before you ask, I have tried reinstalling it quite a few times, but to no avail. I have a legal copy and I've already purchased a serial for the full version although I'm unable to enter it in to validate it.

You must've downloaded this from dowload.com or somewhere.

If you want, download the pk version from crankeye.com, or wait till nouman or someone comes and gives you the keygen thing

Vista is vistastic (vistastic = craptastic).
You're way better off if you don't use it.

Vista is vistastic (vistastic = craptastic).
You're way better off if you don't use it.

Truer words have never been spoken.
Today.
That I saw.

I think he actually bought it with money.

(Bursts out laughing hysterically)
(continues laughing for several minutes)
ok...it's ok...I'm all right now.