When you want to manage your PC's processes, startup
items, network connections, windows, tasks, open files, and installed
software, you can do that all using the free all-in-one monitoring
tools System Explorer. The long list of functionality in System
Explorer's broken down into four categories: Monitoring, Autoruns,
Software, and Settings (they're tabs across the top). From there you
can drill down and manage running processes, files, tasks, and more.
While we've seen a few souped-up task manager type apps (like TaskExplorer),
System Explorer packs in even more features with a small memory
footprint and USB drive-friendly portable version. Check out a few
screenshots of System Explorer in action.

Under Monitoring, here's the Processes tab for straight up task
manager-like functionality, with built-in hooks to ProcessLibrary.com
and Google to look up what the heck a particular running file is,
anyway:

Under Autoruns, here's the Startups section, where you can trim what autostarts with your PC:

Under Monitoring, hit the Performance tab to see live-updating graphs of what's eating up your RAM and processor:

System Explorer is a free download for Windows XP and Vista, portable version available.