a lot of times computers accumulate too much ad ware, spyware, malware, or too many applications running at the same time.
Or it can be caused by a defective wireless router, adapter, poor internet service...
You can work through it, start by plugging the laptop directly into the modem, instead of using a wireless connection or router.
does that solve the problem?
do you share a connection?
Or does it do the same thing when you play DVDs too?
is it dial up, DSL, Cable?? what operating system?