When your PC seems slow, unstable, or you think it might be infected by malware, then your first step should be to take a very close look at the processes it's currently running.
You could turn to the Windows Task Manager, but that provides only very basic information. If you want an in-depth report, something that makes it easy to spot and control unnecessary, resource-hungry or malicious processes, then you'll need to try an alternative.
Here are five of the very best apps available to download.
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1. What's Running 3.0 - Windows 2000/ XP/ Vista/ 7
At the heart of What's Running is a Task Manager-type display of the processes running on your PC. Just clicking a process will display a useful graph showing its recent RAM, CPU and I/O activity (very useful for identifying resource-hogging programs).
And if you don't recognise a process name, right-clicking it reveals a "check online" option that compares its name against an online database of common processes, and will usually tell you more.
What's Running crams in plenty more functionality, though. Its tabbed interface also shows you running services, loaded drivers and DLLs, open internet and network connections, startup programs and basic system information.
The program even provides a snapshot feature to save all this information. You could set a baseline snapshot this month, say, then compare it with another next month to see what's changed - helpful if you're trying to find out why your system is suddenly unstable.
What's Running has one or two problems: we found the interface occasionally confusing, and it won't list the files, Registry keys and other Windows objects opened by your processes. The program does make it very easy to access a great deal of useful system information, though, and it's definitely worth a look.
2. Process Explorer - Windows XP/ Vista/ 7
Launch Process Explorer and you'll see a colour-coded tree view of your processes that makes it very easy to see what's running. And if you spot a name that looks unfamiliar, right-click it, select Search Online, and the program will launch a web search for that process name, so you'll quickly have it identified.
Clicking a process reveals the DLLs and other modules it's loaded, as well as the files, Registry keys and other Windows objects it has open. And double-clicking will display a processes performance graphs, open network connections, thread details and a whole lot more. There's even a Strings tab that displays text strings inside the executable file, very useful if you're trying to identify malware or find out what a particular process is doing.
Process Explorer doesn't have as many extras as some of the competition (no list of Startup programs, for instance), but that's because it concentrates purely on Task Manager-type functionality - it's actually produced by Microsoft. And the end results are impressive: it's lightweight, extremely reliable, and portable, a must-have for everyone's troubleshooting toolkit.
3. Anvir Task Manager Free - Windows XP/ Vista
At first glance Anvir Task Manager Free looks much like the competition. There's a list of running applications here, processes there, and separate processes show you more information about the program you've selected: the DLLs it's loaded, files it's accessing, internet connections it has open, and so on.
Look more closely, though, and you'll find considerable variation in the power and capabilities of each section. The processes tab displays only limited, beginner-level information.
But elsewhere Anvir Task Manager Free also lets you stop or change the startup type of your drivers, a strictly-for-experts feature that, if mishandled, could prevent your PC from restarting, even in Safe Mode. Who's it really for? We're not sure.
Still, there's a lot to like about the program. A well-designed Startup tab gives you control over all the processes launched when Windows starts; a Log window records major PC activity, like processes started, windows created and closed; and bonuses include the "Tweaker for Windows", a TweakUI-type application that provides easy access to more than 100 hidden Windows settings.
4. Process Hacker - Windows XP SP2/ Vista/ 7
Run Process Hacker and you'll see all your running programs displayed in a clear colour-coded tree. If you spot something that you think could be malware, then you can have the file checked by VirusTotal.com in a couple of clicks. And a right-click Terminator option combines multiple low-level techniques to shut down programs that Task Manager alone can't close.
Other straightforward features include a services tab, where you can view, stop and start services; a network tab that displays open internet connections; a Hidden Processes tool detects simple rootkits; and an option to trim the working set of selected processes to help free up RAM.
Drill down to the in-depth information on each process, though, and you'll find some features that are strictly for experts only. Process Hacker not only displays the blocks of memory used by each process, for instance, but it can also change their memory protection settings, edit RAM directly, inject DLLs into a process, create services, and more.
This isn't a program to go exploring if you're not entirely sure what you're doing, then - a single mistake could crash your PC. But if you're an experienced Windows user, or just happy to stick with the basics and leave the advanced features alone, then there's a lot to recommend Process Hacker. It's one of the most powerful and accomplished Task Manager alternatives around.
5. System Explorer - Windows XP/ Vista/ 7
System Explorer provides access to an amazing amount of technical data on your PC. There's the usual Task Manager-type display of running processes; lists of loaded services and drivers; details of loaded modules, and currently open files; and lists of open internet connections, IE addons, Explorer shell extensions, software uninstall programs and a whole lot more.
It could be overwhelming, but a well-designed and attractive tree-based interface makes it easy to find your way around.
The program is particularly good when it comes to identifying mysterious processes. In a couple of clicks you can look up a process name in its own database, at ProcessLibrary.com, Google, or upload its file for a malware check at VirusTotal.com or VirusScan.jotti.org.
A useful History module displays more details on exactly what your programs are doing: processes they're launching, files they're using, internet connections being opened and closed. And a Snapshot tool saves the details of your current running processes, services, drivers and so on. You can then compare your system with a snapshot a few weeks later, and easily see what's changed.
There are better pure Task Manager replacements here. A double-click in Process Explorer, for instance, will display far more information about a process of interest. But if you're more interested in general system management than low-level technical details then System Explorer has a lot to recommend it.