How do I reinstall/ update my Windows XP?

I have a seriouse Virus or adware Problem, I already tried every kind of antivirus and antispyware and nothing helped me agianst those websites that still keep poping when I try to get online, my laptop is too slow now so that it takes me minutes to upload windows. However I decided to reinstall my Windows xp ( of course I will back up my data first but I don't know how I reinstall Win. Xp ? is it free? I don't have a CD anymore can I download it online? Please help me and I will 10 POINTS and 5 stars

How do I reinstall/ update my Windows XP?free spyware

If it was a legit copy of xp, then you should be able to get microsoft to send a new one or provide you with a download link. If it wasn't legit, then you have to buy one.

How do I reinstall/ update my Windows XP?live update

To re-install Windows XP , you will require a bootable cd.

You can download a windws xp installation cd in vob format and burn it on your cd and then install. However this is not legal.
I have done this a couple of times in the past. Can you get around at all on your computer? Can you access info? If so, you should call Microsoft directly and tell them that you want to reformat your drive and reinstall XP. It will cost you $30 or so, but it is worth it if you need the help. They will probably have you look into your computer to come up with your current XP registration code to double check to make sure that your copy of XP is valid. They should be able to walk you through the process and after the reinstall is complete, any viruses that you have should be eliminated. Of course, your drive will be wiped clean and it will be similar to having a new computer, so make sure you back up the vital info. Best of luck.
u should check wheather it is dead necessary to install xp.or u can check yr system throug any other route.i.e-installing antivirus.or u may use system restore option on yr computer.after that if u r not able then u can choice foer format.