I don't want to come off as ranting in response to your first-ever post here, but you're violating the very first, most basic principle of IT security, the privacy of passwords. HR is completely correct, and the policies they are advocating are standard IT practices. Not only should IT not have any users' passwords, neither should an employee's supervisor, co-workers, or anyone else for any reason.
If you know a user's password, you leave yourself vulnerable to charges that you used that account to alter data, send falsely attributed e-mail, etc. You have no proof that you didn't log on as a supervisor, send an e-mail to HR raising your buddy's pay, log on as HR user and respond to the mail by raise his pay, and get a kickback. You have no proof you didn't log on as head of research and forward new product plans to the competition. All anyone has to do is fake a call for service, wait until you log with their password and finish the call, then immediately send an e-mail to the boss telling him ingest feces and cease respiration. "Oh, Jim-Bob was working on my computer at that time. He has my password, he must have sent it." What if that user has the same password for his web mail, ATM, or credit card? If a member of the IT staff gets fired, what's to keep them from sneaking back in and logging on as a user to destroy data? The examples are literally endless.
For these same reasons, there is no excuse for HR to have user passwords, unlike pysces83's company above. If the HR manager to take a dislike to someone, he could log on as that person and start deleting or altering data. All the logs are going to show the account name that entered the transactions, not the person actually using that account.
In short, your @$$ is hanging out in the wind. It doesn't matter how many employees, computers, company annual income, whatever. If I worked where IT or HR had my passwords, I'd be getting my resume together. If I had an IT employee who required users to give him their passwords, I'd fire him.
There is no reason for an IT professional to need user passwords to do his / her job. You should be able to work on a user's computer with an administrative account. This account should be separate from the account you use on a daily basis for your own e-mail, file access, etc. If you absolutely must be logged on as the user to solve a problem and absolutely cannot wait until the user returns, ask the supervisor AND HR to request you change the user's password. This should be in a documented format and require the user to change the password on his / her return.
Edited to blatantly bump this back up the list one last time. tommy needs to hear this from others than jd and I.