Please consider that according to your system specs, you have Vista Basic so almost every proposed solution here that requires secpol.msc or gpedit.msc (and several do) can't be done on your system. You can make direct registry changes, but not using these methods (you can use regedit.exe if you know the proper keys to modify, add, or delete but I saw none that provided what you need for this if such a fix exists). Some of the methods in some of the tutorials might work, but I suspect they won't because those settings and controls are being overridden by the security policy (but the one to disable UAC may work if you do so only long enough to remove the password and then enable it again - but I don't know if that will work in the long run or even cause you login problems where you can't login at all with no password or even with the original password and with only one account you may have quite some problem recovering - difficult at least, but hopefully possible). You also really don't want UAC permanently disabled - it's a valuable security tool that helps protect your system.
How do you have your system configured to boot (do you have a welcome screen, do you use CTRL-ALT-DEL, or do you automatically startup)? How many accounts are on the system (still only the one Administrator account)?
One option (a bit of a hassle but that might work) is to create another Administrator account with no password and see it that works (if it allows it to be created without a password and then if you reboot if it allows you to login without a password). If it does, treat the situation as if the old account were corrupt and move everything to the new Admiminstrator account. To do this use http://windows.microsoft.com/en-AU/windows-vista/Fix-a-corrupted-user-profile. Then use the new account from now on and delete the old one. Now your account will no longer have a password again. Not elegant, but if the system allows you to create an Administrator account with no password, this might work.
I hope this helps.