First, does the specific Microsoft mouse that you are using have any Mac-compatible drivers available?
Secondly, can you test your machine with another mouse, and see if it works OK?
Third, for OS 10.10.3, there were actually
two updates that came out. What you could do is to apply both of them. They are the OS 10.10.3 Combo Updater, and the OS 10.10.3 Supplemental Updater. You can get each of them from the following sites:
Combo Updater:
https://support.apple.com/kb/DL1804?locale=en_US
Supplemental Updater:
https://support.apple.com/kb/DL1807?locale=en_US
Make sure to apply the Combo Updater
first, then apply the Supplemental Updater.
Not sure if it will help with your issue, but at least you would definitely be up to date as far as the OS is concerned.
By the way, I have a late 2012 Mac Mini, and I use a Logitech USB mouse with it (Model M310), and it has a USB Connector to one of my USB ports. It works flawlessly (although I don't use Dashboard). For now, one can get a new one for about $15. It does come in different colors (I have a grey one). Not sure where you are located, but here is some info/pricing:
Logitech site:
http://support.logitech.com/product/wireless-mouse-m310
Amazon:
http://www.amazon.com/s/?ie=UTF8&ke...vptwo=&hvqmt=b&hvdev=c&ref=pd_sl_5ouwbizhfu_b
Best Buy:
http://www.bestbuy.com/site/searchpage.jsp?st=Logitech M310 mouse&_dyncharset=UTF-8&id=pcat17071&type=page&sc=Global&cp=1&nrp=15&sp=&qp=soldby_facet=Sold By~Best Buy&list=n&iht=y&usc=All Categories&ks=960&keys=keys
Walmart:
http://www.walmart.com/ip/Logitech-Wireless-Mouse-M310/14301744
Staples:
http://www.staples.com/Logitech+M310+Mouse/directory_Logitech+M310+Mouse?