[UPDATE: Google closed up 1.48%; Microsoft squeaked into the black just before the bell, closing up 0.13%. On Thursday, as the news has sunk in, Google closed up 2.8%, and Microsoft down 0.53%.]

Tech writers are mostly dubious about Google’s attempt to challenge Windows head-on with ChromeOS. But investors are voting with their wallets. Here’s how the two company’s shape up.

In late trading today, Google shares (NAS: GOOG) were up 1.42%, defying the Nasdaq’s negative trend for the day.

Microsoft shares (NAS: MSFT) were down 0.25% and shaping up to close around the $US22.40 mark after dipping as low as $US22 during the session.

Last night, Google announced ChromeOS, which will be initially aimed at netbooks but has broad x86 (Intel PC) and ARM capability that will allow it to run on any PC. It will be released in mid 2010.

NBR is bullish on ChromeOS’s prospects (see our take here) but many tech critics are more dubious (read 5 reasons ChromeOS will fail at pcworld.com).

Google and Microsoft by the numbers
(Courtesy of WolframAlpha.com; see more stats here)