This might be an impossible question to answer remotely but I figure there may be some common causes that people can suggest so I think it's worth asking...

Video no longer plays smoothly on my laptop. It used to but not for a while now. For example, playing a video on YouTube is pretty typical: I press play (making sure it's not on HD or even HQ) and the video buffers a little then starts to play. At first it plays fine then the video starts to stutter, turning into a slideshow while the sound continues to play smoothly. If I try playing the same video on my Playstation 3 (which is linked to the same network) it plays smoothly so it can't be the connection.

Another example is streaming DivX videos. Again, I wait while it buffers and it starts but very soon, instead of a slideshow, this time the video just plays slowly while the sound continues as normal (instantly getting out of sync). Even if I let the video fully load before pressing play (i.e. it's no longer streaming), it still behaves the same way. I can even let it load 100% then save the file to hard disk and use VLC player to view it, and the same thing happens.

I'm using an old laptop running Windows XP. For the past several years it's been connected to the router via Wi-Fi but in the past few days I've changed that to a network cable (like my PS3) but that hasn't helped. Yes, I regularly install various bits and pieces of software but nothing that I can identify as being the cause.

So, are there known causes of this sort of behaviour and if so, what can I do to fix it?

Thanks.

Update to answer a few questions...

Laptop Spec' (note: video has played back fine for the majority of time I've had the laptop)

• Toshiba Satellite 1900-603 (possibly called something else outside the UK)
• Intel Pentium 4 2.2 Ghz Processor
• Originally had 512Mb memory but recently doubled that to 1 Gig of memory
• Graphics: ATI Mobility Radeon 16Mb DDR VRAM
• Windows XP SP3 (Home edition)

Over the years I've done several things to speed it up (disabling indexing etc) and am generally happy with the performance. I also regularly have a clear out of old software (if for no other reason than the laptop only has a 40Gb hard disk) and use CCleaner and Glary Utilities to strip out much of the crap from my system.

Also recently (after doubling the memory), I've tried a few new things which might be likely candidates for slowing the video down such as Rocketdock, Jingle keyboard (which gives an old style 'clacky' typewriter sound when I type - love it), SugarSync, Taskbar Shuffle. However, the video doesn't play smoothly even when I try quit all these apps.