The blocking is probably being done using the browsers user agent string. You can change the user agent string using the --user-agent command line argument to impersonate IE8, for example use the following.
"C:\Documents and Settings\\Local Settings\Application Data\Google\Chrome\chrome.exe" --user-agent="Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0)"
This of course assumes they are allowing IE8 :-)
However, even if this works, you should check your companies support policies as you may be breaching them.
1What's the point of blocking Chrome ? If at all, they should block MS Internet Exploder – Quandary – 2010-02-27T09:22:59.270
Excuse me for asking, but do your IT dept, have a valid reason for blocking Chrome Specifically? – JL. – 2009-09-29T07:03:17.250