Missing links on the scren

Hello
From one day to another (26. -27. of may)all the the links I have placed on the screen (XP) have no functionality anymore. Using Bullguard and Lavasoft Ad-aware. Any links from start – programs are useless. Via the link to internet connections I have been able to activate my adsl-connection and further more the internet-explorer icon has been active on the screen. Through that gateway I have been able to reach the mail box of my first class client’s internet access. What has went wrong with the total failure of functionality of the link system on my computer?
Keld Jegind
Denmark