laptop gone so slow overnight

[leo9902]

My laptop has been running ok until the last few days when now it is nearly impossible to get on anything even internet ex. or firefox can take half hour or more to get on and then its painful waiting for any others sites i want to go on. Have borrowed another laptop to see if it is my broadband thats the problem but got on fine and no problem searching with it so this means it must be a big problem with my laptop and ive no idea about computers so is it a computer repairer i need ? I ve read where you tell people to do certain things to try and clear things but with it being so slow that dosent seem an option for me .How can this happen more or less overnight its so frustrating.

[Jumbuck]

Is the hard disk being hammered? Or is it just the internet connection which is running slow?

[hc4361]

Vista? XP?
How does it run when you connect by cable?

[beso]

Anti virus programs? If you are running two the computer will often grind to a halt.