I have a link from Microsoft but the page linking to me has a rank of 0, does this still help?

Every link helps but the most impact comes from pages actually related to the topic of your website. So if you have a travel site, links from hotels, car rental companies are always good for example.

I know how it works generally but I don’t quite get this calculation.
PR(A) = (1-d) + d(PR(t1)/C(t1) + … + PR(tn)/C(tn))
And ‘d’ is a damping factor that’s usually set to 0.85. What’s a damping factor?

You’ve obviously stumbled onto someone’s "home-grown" page rank calculation. Explaining this calculation wouldn’t provide anything meaningful to you because whatever this formula calculates, it’s not actual page rank.

Page rank is fluid and evolving. There is no formula to calculate actual page rank. The best estimates could only give you an "average" rank. People have come up with formulas to estimate page rank, which is a little more accurate then weather forecasters.

The only known factors, in determining page rank involve the following:

1) Backlinks: Website popularity – number of established, credible links from other sites to yours. This accounts for most of a page rank calculation.
2) Domain Longevity: Longer your site has been around, the better the chances of ranking. When competing in search, domain longevity can move your site above other, younger sites.
3) Domain Origin ( Global, Country, Sub-Domain ). There are country specific domains, such as .us that target only visitors from the US in search. Conversely, there are global domains, such as .com which target a world wide audience.
4) Website Content: keywords and text.
5) Website CTR Rate in Search. If your website continually interests visitors, via the number of times a searcher has clicked on your site in search, then it will begin to move up in page rank. This is valid for both personal search history ( google personalizes its search results to individuals ) and google search history.

All of the factors above, and more, are used to determine a website’s page rank.

Google, through its available tools, provides a great deal of information, which could be used to estimate page rank. However, Google does provide that information anyway – a detailed analysis of search result history ( Google Webmaster Tools ).

I’ve seen conflicting views on this topic with some saying Wikipedia links are beneficial and others saying that Wikipedia links are all no follow and don’t help pagerank. I’m just looking for clarification. Thanks

Page rank is a view of how popular a website is to the search engines based on the amount of incoming links from other sites.

When you see a site using the nofollow tags it’s simply telling the search engines not to follow that link since they cant, or don’t want to, vouch for it. If they didn’t use the nofollow tag they would be telling the search engine to take some of that pages link juice and give it to the page they are linked to. Since Wikipedia wants to keep their page rank as high as possible they use the nofollow tag to keep the link love on their sites pages to ensure they help their page rank.

Even though you may not be getting link juice from the backlink you have at Wikipedia it’s still one of the most popular sites viewed online. So even though the search engines don’t count it as a backlink to your site it’s still a link on a very popular site that can bring you lots of targeted traffic.

So i a nutshell no, inbound links from Wikipedia DO NOT help your site’s page rank but it’s still a link that, depending on the site (Wikipedia), can bring loads of targeted traffic.