With TrueCrypt, there's no way to get rid of the pre-boot authentication process - it has to have a strong password or passphrase or it provides absolutely no protection at all.
Simply put, if the staff can boot into Windows without interacting with TrueCrypt, then so can someone who steals the computer, and that person can also decrypt the drive at their leisure.
If it's an issue of convenience rather than trust, you might consider having a YubiKey programmed with all or part of the TrueCrypt passphrase - these can be quickly inserted into the computer to complete a reboot, then locked up in a desk drawer or safe until the next time they are needed.
Otherwise, if you want the system to boot directly into Windows while still using full disk encryption, you'll need another solution. BitLocker+TPM+Secure Boot comes to mind in a Windows environment as an obvious option, but be aware that you may have to make some configuration changes to have a reasonable level of security - at the very least restrict access to the BIOS, block booting from removable drives, and insure that all Windows recovery options are configured to require an administrator's password. The obvious downside to this is that it requires hardware support within the motherboard itself.
If the issue is trust, or a policy requirement to not have shared passwords, there are various commercial encryption products out there that have different options for the pre-boot process. Some of these can authenticate with a server on the office network, so that the computers boot freely when used within the office, some of these offer robust user management, so that everyone has their own credentials to boot the system, and some of them offer support for hardware tokens - smartcards and USB dongles. These are enterprise-oriented features, so the products that implement them generally don't come cheap, but they are out there.