Why Use Software to Audit?
     
Save time
An IT professional may be able to determine roughly what software is installed on a PC with only a few minutes work. Most applications will have icons with text saying what they are. But it is not so easy to tell exactly what version of an application is installed - it's usually necessary to run the program or investigate the executable using Explorer. For a PC with 10 applications or more this is no longer a simple task.

One other thing to consider is that when an engineer arrives to look at someone's PC they will often be asked "while you've here, can you check why my (printer) doesn't work properly"!

The actual time taken will depend on the skill of the engineer and the quality of data required, but in an office with 50 PCs some overtime may be necessary!
 

Avoid disruption
Unless you're working outside office hours it will be necessary to ask users to give access to their PCs - you'll be surprised at how many are in the middle of producing a vital report....
 

Be more accurate
Occasionally users will simply copy program files over the network, or remove shortcuts from the Desktop and the Start menu. There will be no visible sign of the product, but licenses are legally still required. Explorer can find all ".exe" files, but this will typically produce between 500 and 3000 results - it's not practical to examine every one. Directory names can sometimes give clues, but are not a reliable guide because they can almost always be changed at install time.
 

Keep it up
And of course as soon as you've finished a manual audit your users could be busy installing whatever they like. Given the time taken to carry out a manual audit they know you won't be back for some time!

Audit tools provide a way to regularly collect and report installed software from a central point. Purchasing or renting remove audit software will almost always be less expensive than conducting a manual audit, and will also be much more accurate.
 

But audit tools are not all the same!

Some tools will completely miss important installed products, other tools will report hundreds or even thousands of secondary or utility executables as separate products. Auditors need accurate reporting to have any chance of success - this web site explains how Aperio achieves this goal.