Computer will not complete boot up process. Returns to bios check from the welcome screen. Any suggestions?

Does it get to the Vista splash screen at all ?
If so might be worth trying a system restore on it.

Any changes that either happened or that you perhaps made to your computer around the time that the problem started; particularly any software or hardware that you installed or setup.

You can try going into BIOS and resetting system defaults and save changes to see if will boot after changes made

You may need to reinstall windows vista on this computer because this can be a corrupted operating system...