What's making my disk thrash in Windows XP?

I have a sick Windows XP laptop; something's making the disk thrash and the entire system is sluggish to unresponsive a few minutes after boot. How do I figure out what is making the disk thrash? Task Manager is fine for finding what's using the CPU or memory, but doesn't show disk I/O.

Details: running Win XP Home, the machine was working fine until a few days ago. I've verified it's not paging because it's out of RAM. There's no scary SMART errors according to DiskCheckup.

Download Process Explorer from Microsoft / Sysinternals.

Run it and click view > Select columns. Click on the Process Performance Tab, and select "I/O Reads" and "I/O Writes".

You can do this from Task manager, but I prefer using Process Explorer.

You can then sort by these columns and see what is doing the most read / writes.

(if using Vista / 7 remember to run as ADMIN (or click file then "show details for all processes" which will do this for you)

I tend to find that Dropbox and mesh on a few machines I support seem to run wild with read/write bytes 24/7 so if you use any sycn software, first bet is to look at that, however running this tool should tell you exactly what is wrong.

In addition, you can click on any of the graphs at the top of the screen which brings up a "System Information" dialog of historic information. One of the graphs (third one down) is "I/O Bytes", Simply hover your mouse over any of the peaks, and it will tell you what is taking up the most resources. - Exactly what you want!

You can set task manager to show each applications Disk I/O. Navigate to:

View -> Set Columns

this dialog will pop up, check the disk read & write i/o boxes: