My task bar is blinking? what's the problem with

If the buttons on the taskbar are blinking, that only means that there is another application in the foreground hogging all system resources - CPU or memory or disk - so that a background application can't get to the foreground immediately (also, you may have a foreground application which has been instructed to STAY on the foreground (e.g. a video player)).

So to notify you they want to tell you something, the applications will blink their taskbar buttons. Click on the buttons to transfer system attention to those applications and let them say whatever they have to say.

To know which programs are hogging the system (if any), in XP you can press Ctrl-Alt-Del to display the Task Manager and sort programs by CPU usage or memory usage. More sophisticated hoggings may only be diagnosed with more advanced programs such as Microsoft SysInternals Process Explorer.

Usually, however, it's not worth the hassle. Just wait some seconds for the tug-of-war to resolve itself. If it doesn't, kill the stuck application from Task Manager. if the problem represents frequently with the same app, then you may have a problem with that app, and a more detailed diagnosis must be done. If many programs have this behaviour, you might have a slow disk (too fragmented? Defective? Check with PanteraSoft HDD Health, defragment with Defrag) or some hidden process eating resources (virus - you need an antivirus).