Should I delete files in the Prefetch folder if my PC is running slowly?

Q My Windows XP seems to be running very slowly these days – sometimes I seem to be waiting for it to catch up with me.

One file that seemed to be hogging all the processing time appears to be ALG.exe. A friend advised me that to speed up my PC, I should delete this and other spurious files. Indeed, he advised that I delete everything in a folder called ‘Prefetch’.

I found this folder and it seems to obtain links to all the programs I have opened since year dot. Is it safe or even wise to clear this folder?
Brian Withers

A Never, ever delete files just because they seem to be taking up a lot of the PC’s processing time.

We assume that you used Task Manager to finger ALG.exe as a potential resource-stealing culprit? If not, try this: right-click the Taskbar, choose Task Manager then click the Processes tab.

This provides an insight into everything your PC is running at any given moment, along with the name of the program file, the processing time consumed and the memory used.

However, it is important to understand that this list is dynamic. Even undemanding applications, such as Notepad, say, can briefly consume huge amounts of processing time. Other programs may be more consistent in their processor use, while still more fluctuate constantly.

The point is that in order to draw any conclusions this list must be watched for a while.

To sort the entries, click one of the headings at the top: click processor, for instance, and you can instantly see which programs are demanding most of the processor’s attention.

If one entry seems to be consuming a disproportionate amount of processing time then it may be worth further research.

Use a search engine such as Google to look up the file name and read about the experiences of others. Don’t worry about the ‘System Idle Process’, by the way: this is just Task Manager’s way of reporting that the processor is busy doing nothing.

This brings us back to the ALG.exe file, mentioned in your email. This relates to the Application Layer Gateway, which is a legitimate Windows service. It is associated with internet access and helps certain applications navigate through the Windows Firewall to connect to the online world.

However, like many a legitimate Windows file, ALG.exe has become a target for virus authors: ‘trusted’ or recognised file names like these can provide a cloak of authenticity for electronic miscreants of all varieties.

If you have reliable anti-virus software installed then it is unlikely that ALG.exe has become infected. But if you don’t, and ALG.exe is persistently riding high in Task Manager’s CPU column, then it is possible that it is a spyware application masquerading as the real thing.

The most important thing to do, then, is to ensure that you have up-to-date anti-virus software installed: the free version of Anti-Malware from Malwarebytes is becoming increasingly popular with Computeractive readers.

Finally, forget your friend’s suggestion of emptying the Prefetch folder to receive a performance boost: this is a well-worn myth that has been thoroughly debunked.

No performance improvement will come of deleting everything in the Prefetch folder. Indeed, the reverse is true – the PC could slow down until Windows has repopulated the Prefetch folder.