Q: Some of the email attachments download but won't open or run. A message comes up "Windows cannot access the specified device path or file. You may not have the appropriate permission to access the item."  Am using XP Pro and have PPP and Adobe Acrobat installed. I have tried to download Google Chrome with same result.

A: This error is because you may not have the appropriate program on your computer to open the type of attachment that was sent to you.

To find out what program is needed you must look at the file extension which are the last three characters of the filename after the dot. In order to see that extension type in Windows Explorer, you must click on Tools, Folder options and remove the tick from “Hide extensions for known file types”. Then you must associate a program with this file extension.

If you still do not know what program is needed, and this requires knowledge and experience, then look at: http://filext.com  to identify the correct program and then open the attachment using the appropriate program. If you do not have the required program installed you should ask your sender to use another format, if possible.

The association is done from Windows and the wording on the dialogues boxes will vary a bit depending on version of Windows.
To re-associate a file type, do the following:
·    Highlight the wanted file with a mouse left click
·    Right click on the selected file
·    Select Open With then select Choose a Program
·    Select the required program from the list and check the “Always open with this program”

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$NTUNINSTALL files

Q: Whilst trawling through my files yesterday to find the Firefox bookmarks, I came across my Windows XP directory and found that there were a huge number of files $NTUNINSTALL...followed by a series of different numbers. I know these represent Windows automatic updates but are they worth keeping? Some go back over 4 years! I assume that other readers of your excellent column have the same query.

A: Quite a number of readers have asked this question.  According to advice from a senior Microsoft developer these files should not be deleted. However, I asked that question shortly after XP was released and the underlying principle is the same even now. These uninstall files relate to security and other patches that have been automatically installed onto your computer and will be required in case you wish to roll back to some earlier point.

As you are unlikely to go back to a 2005 or even a 2006 version, all early folders can be deleted. Caution; be careful not to delete $hf_mig$ which has the date of the latest update performed on your computer. The folder itself may have been created a long time ago but the contents keep changing and it will be used for future updates.

I have deleted all but the current year on my test computer and there have been no problems, but this is a sample of one and I do not place too much emphasis on it. If you have very many GB free on your drive and the backup drive has adequate spare capacity then I would not bother deleting these. If your computer is stable then deleting all but the current restore point may free up more disk space. This is something that I do every few months.

To perform this action open Windows Explorer and right-click on drive C, Properties, Disk Cleanup then click on the More Options tab and select System Restore and Cleanup. Answer Yes and click OK.

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Banking on Wireless security

Could you please tell me the best security for a laptop connected by wireless to the Internet? I do all our banking and paying bills on the computers.

There are a number of steps that you can do in order to make your network quite secure. These are:
·    Firstly change the default administrator's router password otherwise if a hacker gets in, he or she can do anything.
·    Then enable WPA2 (Wi-Fi Protected Access 2) encryption and use the highest level available, typically 128 bit.  Periodically change the WPA2 keys.
·    Alter the SSID (Service Set Identifier) so that the default is not used and ensure that all computers use this SSID. Most wireless routers broadcast the SSID every few seconds as this is intended to allow clients to dynamically discover the wireless network.
·    From the router, you should disable the SSID broadcast, as once set up in your home it is not necessary to keep broadcasting it. This will prevent casual users from finding your network.
·    Enable MAC (Media Access Control) address filtering. A MAC address is a 12-digit unique code assigned to each Ethernet card. This will only permit access with that specific MAC Addresses to access your router and deny network requests from any other network card. To find out the MAC address of the your laptop, open a DOS box by clicking Start, Run and enter CMD then in the DOS box type IPCONFIG /ALL and look for the line Physical Address. . .and enter the characters such as 00-60- 67-76-FC-EF for the permitted user into the wireless router.
·    Finally, ensure that you have enabled your firewall.

Although no wireless network can be considered to be 100% secure, I feel that if you have enabled all of the above steps you are quite safe doing banking on the Internet.