I suppose the obvious thing to do is return it to the Vendor and swap it for a working machine. Or at least notify them that you have a problem.
Try running ChkDsk to check your drive for errors. Right-click your Drive icon/ Properties/ Tools/ Error Checking. Select both boxes.
If you want to have a go at fixing it yourself then it may be harder to return it then than it already may be now.
Will it Start and run correctly in Safe Mode. Can you check out how it runs if you login as any other user in Normal Mode?
To get further information about the error look in your Event viewer.
Look in the System or Application folder. You can get to the Event Viewer via right click My Computer icon and select Manage.
Any errors logged in the Event Viewer can be expanded by double clicking on the error line.
Take any event error I.D. number and search for it on these sites.
If the error occurred after installing a device driver or application, try using Safe Mode and removing the driver or program.
To check your RAM.
To check your Hard Drive further than ChkDsk can.
The drive manufacturer will have free diagnostic software to check your drive for problems.
Any errors in Device Manager?
To check conflicting software, most of these apply equally to Vista.
310353 - How to Perform a Clean Boot in Windows XP
316434 - HOW TO: Perform Advanced Clean-Boot Troubleshooting in Windows XP
310560 - How to Troubleshoot By Using the Msconfig Utility in Windows XP
Removing adware & spyware
faq608-4650
Will check your computer for spyware and adware.
See if you have any services that are flagging as "Starting" but not actually running.
Some general things to try.
See if System Restore will get you back to a restore point before your problem with Windows.
Run the System File Checker program from a command prompt by typing.....Sfc /Scannow in it and have your Vista DVD handy.
If they don't work you could try repairing windows itself by running it over itself. You will lose all your windows updates but your files will be untouched. Links in this article.
Windows Help and How-to
Check what Repair or Recovery options are included with your actual machine if you were not given a retail DVD but have a Recovery type DVD.
Like I said, don't waste your time fixing faulty machinery that ought to be returned and a refund obtained.