HP is schizo in so many ways... good memories. I used to catch some guff from my HP local DM while being an in-plant for a certain Nordic company that didn't have ANY dress code (Viva Suomi! Haakka päälle!!!) so we had a lot of fun needling her about being the only squares in a young, boisterous environment (my HP US managers didn't seem to mind, given that they were all engineers, hands-on nerds and went to work in 40-degree Texas heat in the summer)
That meant totally contradictory "dress codes" depending on which country you had an answer from... we ended up wearing whatever we wanted, and since the work implied everything from setting up routers and switches to actually moving and racking these routers & switches across Mexico City, I ended up wearing army surplus every day and once won a Halloween party contest in my unaltered work getup!
Professionalism? Like I told a HR interviewer once "The moment you find a tie that gives you a Cisco cert just by wearing it, call me! I want to buy some..."; habit and cowl does not a monk make, and if you want to look formal in an IT department, the old standby from the mainframe days is always available, highly practical, much more resistant than suits and ties, and impressive as hell: white lab smocks, preferably with company logo sewn on.