My computer makes a highish pitched whirring noise every time it has to do something slightly difficult, typically a video or interactive things. What is it and can I fix it?

Hi

as long as there is no issues with normal operations -- nothing to worry about .
That high pitched whirring sound is likely the hard disk drive ... if it's a low rpm drive (ie: 5400 RPM) it is working overtime to catch up to the demand in multitasking-- that whirring sound is actually the spindle or disk inside the hard drive spinning

HOWEVER, it appears as though (depending on the exact part # of the computer) , you have eithet 160G or 200G hard disk drive, which runs at 7200 RPM.. one or both of the models has the Seagate quiet drive .. you may have the other which is obviously not so quiet

nothing to worry about, but to prevent any issues --

make sure that your system is frequently de-dusted,, especially the power supply fan and the CPU heatsink fan. DO NOT BLOW ANY AIR into the fans without placing a small instrument to prevent the "fins" from spinning., insert something in bewteen the fins before blowing air into the fans to release all the dust.

extra cleaning measures prevents issues and extends the life of the systems peripherals.

hope this helped you !

Yes, open the side cover and determine where the noise is coming from - Harddrive, fans, DVD/CD player, etc.. If it's the harddrive, start backing up your important data asap before it goes out completely. If it's a fan, power down the computer and clean the fan. If it's t DVD/CD drive, replace the drive.