Right, my 2 year old macbook is playing up – it's pretty slow and very fond of crashing – its most annoying habit being crashing every time I try to run iTunes and failing to back things up to a hard drive.

Obviously anything at all could be causing any number of problems but is there anything simple I can do that might help? Ideally some sort of 'restore to factory settings without totally f'ing up my stuff' function, although I get the impression it won't be that simple…

You could try booting from your install cd do a reinstall of the OS, you'll get the option to put all your current documents into a separate folder after install… that's what I'd do anyways, sure someone else will pop along with a better idea.

if you want to rule out software, back up and format and reinstall the operating system,

if you want to rule out hardware the things that will die are harddrive, ram and then motherboard, if its the last one then its a cost thats more than your laptop is worth, if its the first 2 then its about £80-100 to fix yourself.

search for hard drive and ram diagnostic tools.

How much space is there left on the the hard drive?

Have you tried – applications – Utilities – Disk Utilities – select hard drive – click repair. It might help.

OS reinstall may be worth doing but as others have said some ropey sectors on your HD might be causing it. Having said that, iTunes can be a hog and cause problems. If it's only that app causing the crashes you could back up your library, delete all iTunes software and preferences and install from scratch.

If you want to repair your HD the OS may not let you run Disk Repair without booting from an install CD – you'll have to put the CD in, restart and hold down the C key (though you need a little confidence as it initially appears to run the install but after OK'ing language etc you can opt to run Disk Utility from the top bar menu). While you have Disk Utility open I'd repair disk permissions as well.

Also in Utilities is the Activity Monitor, which is like Task Manager for Windows. It will at least tell you what's eating CPU, RAM and virtual memory.

You could download a utility tool such as Cocktail, Applejack or Onyx to do some logfile tidying and miscellaneous tasks but I doubt they'd fix a crashing machine. Hope you get it sorted. Back up your data whatever you do (or even if you do nothing)!

applejack should sort it. only need to reinstall the os when things are really bad. (only needed to do that once in 15 years and 7 macs, and that was my own fault not the computers)

What kind of 'crashing' – the program stops working or the machine just gives up? What are the symptoms? The spinning beachball of death? Freezing?

That aside.

'backing up to a hard drive' – via Time Machine or Backup? If you want to keep your stuff then use SuperDuper and clone the drive before step 2.

0. If you bought AppleCare then just call the number and get help
1. run software update & install the updates.
2. boot up from the OS DVD and run Disk Utility–>repair on the HDD. Just like SImonE says
3. run TechToolDeluxe and see what it says

if it keeps crashing then consider an OS reinstall. I've not yet done this on a Mac.

You could try the discussion boards at support.apple.com

Even better, pop along to the genius bar at your local Apple store. The folks there are helpful.