Hope this question is in the right place.
Is there a reccommended order in which to perform disk cleanup, compress old files, disk defragmentation ??
I'm not a big file user, typically 90% free space(67GB out of 74.5GB). but find disk cleanup takes about 20 mins with old files compressed, then defrag takes another 40 mins typically.
I do this about once/month, only because I read somewhere that it keeps the computer more efficient ??
It certainly speeds up internet response for a few days.
Just wondered if I need to do one of them perhaps more or less frequently?

The more often you do it, the faster they will get done. With heavey use, once a week is a good approach. I would do cleanup first, then the defrag.

you might want to try the Defrag program called Diskeeper. very useful. however i believe you might have to pay for the full version.

I agree with Joeofeg - there's no point defragmenting files that will later be deleted by Disk Cleanup. If you're doing it once a month and you reckon you're not a heavy user, it's surprising that you can actually tell a noticeable difference for a few days after you've run it. On this basis, I would suggest that you could enjoy a more optimised Internet experience all the time by reducing the size of the Temporary Internet Files cache. To do this, open Internet Explorer (please accept my apologies if you use a different browser!), go to the Tools menu and select Internet Options. On the General tab, there's a section titled 'Temporary Internet Files'. Hit the Settings button and set the cache size down to 1MB.