|Synaps? Never heard of it. Walmart? I never have and never will buy computers, cameras, anything electronics from them.|
The fact that your SlimLine is new and the loading of the preinstalled Vista gets hunged and Walmart cannot help you - if I were you, I will just return the computer for full refund.
The reason is that any problems that surfaced in the very beginning is a sign of unhappy experience with Vista.
Buying a different monitor may or may not not make the Windows cannot complete installation in safe mode disappear for good. You will have to do some troubleshooting to overcome it.
Save yourself the aggravations - it's not worth it over the long run, especially with your brand new PC.