Shares of Microsoft (MSFT) dropped nearly 2.5% in the opening hour of trading Wednesday thanks in part to a downgrade by Global Equities Research’s Trip Chowdhry that included this bulletpoint:

• 70% of incoming University freshman students are coming with Macs, which is up ~10% – 15% y-y. Microsoft is failing to connect with the new generation of users

Sounds good for Apple (AAPL), right?

It also sounds too good to be true, given that only five years ago Apple’s share of the campus laptop market had dwindled to the low teens. Chowdhry’s note said his estimate was based on a survey of incoming freshman at five universities, but it didn’t say which universities or how many students he had talked to.

So we checked with the best source we could find, a Ridgewood, N.J.-based research firm called Student Monitor that has been tracking higher education computer purchases for 22 years. Twice a year, Student Monitor interviews 1,200 students for 55 minutes each at 100 representative campuses and sells its findings to Fortune 500 companies.

Suffice it to say that Chowdhry’s 70% doesn’t match any of Student Monitor’s figures. Here, according to managing partner Eric Weil, are the facts:

• 95% of college students interviewed this spring owned at least one computer (83% owned a laptop, 24% a desktop, 15% both)
• Among the laptop owners, 27% owned Macs
• Among the desktop owners, 45% owned a Dell (DELL) or HP (DELL) and 14% a Mac
• Among those who planned to purchase a new computer, 87% planned to buy a laptop. And among those students 47% planned to buy a Mac.

That 47% is as close to Chowdhry’s 70% as Weil’s research could take us. But it’s nothing for Microsoft — and certainly not Dell — to celebrate.

As Weil points out, Apple and Dell have switched positions in the college laptop market in the space of five years. In 2005, 47% of students buying laptops chose Dells. In 2010, 47% are choosing MacBooks. See the chart below:

[Follow Philip Elmer-DeWitt on Twitter @philiped]