If you have access to either Symantec or McAfee corporate/enterprise solutions, they are very good. Unlike their home software, they actually work. I use McAfee VirusScan Enterprise 8.5i and I love it.
No matter what you choose, I recommend that you turn off any real-time protection. It generally just slows your system down, and if you are a smart enough user, you don't need it. Instead, use the built in scheduler to schedule daily system scans. Every night at around 5 AM my system does a quick scan that scans all high risk file types (e.g. only EXEs, DLLs, etc). Every week it does a complete system scan that scans absolutely everything on the entire system.
If you really want real-time protection, go with something that will allow you to disable scan on file reading. You only really need to scan files that are created or modified. As long as your system is clean (i.e. you've run a full scan) you don't need to keep scanning files as they are opened. It'll slow you down a lot. The exception to this rule is network drives and removable media. Some scanners may have the option to scan those volumes all the time.
Bassoon, n. A brazen instrument into which a fool blows out his brains.