Alright, I scanned the file (can be found here:
http://customize.org/rainmeter/skins/62898) with NOD32 AntiVirus and Malwarebytes Antimalware (both updated), found nothing. Uploaded to VirusTotal website, which uses a bunch of different detection methods by different antivirus programs, most of them junk, and came up with like 5 out of 30 detecting something, this usually means a false positive, as they each detected something different lol.
I also researched the problem on the rainmeter forums, a few people have had this problem with other popular skins, and even rainmeter itself, because they use a developer program called AutoIt for compression of some files and that is recognized as a virus by some anti-virus programs. I looked inside the darkrainmeter.zip skin folder, and sure enough there is an .exe for the skin in one of the folders that has a logo with a big "A" on it, that looks like the AutoIt logo. So, 99.999% it's a false positive, as malwarebytes and nod32 are the two best antivirus programs out there (because both are updated relentlessly, and don't have all the bells and whistles of reminding you that they're there just to make you 'feel' safe, as so many AV do).
Alot of those home-oriented AV programs, especially the ones that nag you, like to include everything in their detection-updates to score better on AV comparison tests, but really 'detection rates' mean nothing, as you could class every file in the universe as a suspicious malware and get 100% detection rate and beat everyone else, and as far as I know the tests don't care about this.. It's kind of the same deal as milk cereal and processed food advertising in our domain, while it seems like the holy grail of the food world because of all the press, it's really not... Malwarebytes AM and NOD32 AV both run automatically, silently, and never bother you with more than one window even if something is detected. The absolute best protection, though, is to run programs that are suspicous through 'sandboxie', which kind of allows them to run in a quarantine environment, so they can't spread if they are a virus.