In reply to The Lemming:
> Now what was hogging my computer?
Lightroom?
Seriously, last time I tried a huge batch operation, it had some bugs when working with big sets of files. And you are using an older version.
Check your startup disk free space when you next do a big convert in Lightroom. There was this bug in PS & LR where it would write invisible temporary files into a really well hidden system folder (even when it was configured to use another drive as cache and temp location!) and it would hog up all the space on the startup drive. Only reboot helped.
That bug would not be much noticeable in normal operation, but when doing really intensive batches (like multiple merges to HDR), suddenly tens of gigabytes would "vanish" from the startup drive, even filling it completely, until full reboot.
I saw that bug in later versions, so it might be worth a check?