How safe are free screensavers?

I'm running Vista Home Premium with ESET NOD32 along with SPAMfighter pro. I see a lot of free animated screensavers. I imagine you would get spam if you used one but I'd like to know how safe they are. Also, I like one of the MS Windows 7 screensaver on my brother's new laptop. Is there a way of copying that screensaver and use it with Vista or does MS make it impossible?

Most of the time I just use MS's bubbles screensaver so I can see if I have any new email.

Thanks for any input!
Mike

In recent years, downloading desktop wallpapers and screensavers have not been a safe bet. That's not to say there aren't clean ones out there, but I would argue that most(?) sites are questionable at best. If you end up getting some "safe" recommendations, I'd still test them at something like VirusTotal http://www.virustotal.com/ At least that way, you stand a better chance at not getting an unexpected PC "guest".

As for transferring screen savers, you can try copying some of the .SCR files from 7 to Vista (using the correct paths (like C:\Windows\System32) of course.) They may work, they may not...

Even if I only have 0.5% suspicion that something could be dodgy I always run it in a virtual machine first. That's one of the great things about virtualisation, the VM is sandboxed from the host OS and so can't hurt anything :)

Thanks for the info on virustotal.com and I'll probably stay away from the free screensavers. I can always buy them at Best Buy for $20.