Max, there's many things you can try. The first is to add RAM which I understood you've already done. 2 GB for Win7 isn't really much, but a 32 bit OS can't handle more than 4 GB and the system will show only some 3.5 at the max. What next?
I've had a very good experience with CCleaner, it's one of the first tools I use on a slow rig,
but since we're talking about a business computer, I'd recommend some precautions. You said you have backups made, but I'd like you to take it one step further: Make a clone of your existing hard disk just in case something goes awry and verify the clone's functionality before attempting any speeding tricks.
Now that you have an identical hard disk to save your bacon in the worst scenario, let's start playing! You might want to start with built-in Windows tools, for which this gives quite a thorough list to go through:
http://computerstepbystep.com/pc-tune-up-windows-7.html. The most important ones to do is to run a Disk error checkup (chkdsk /r), do a Disk cleanup for temporary files (cleanmgr) and check Windows system files integrity (sfc /scannow). Resetting the browsers won't hurt, either, and while you're at it tweak the settings so that they won't gather unnecessary crap. After a thorough cleaning there'd be need for a proper defragmenting, too.
As I said, CCLeaner has proved to be a reliable tool and despite your Google search results it hasn't caused trouble lately, not in several years as I know of. I've seen some other similar products cause issues, though, so your findings are relevant. There used to be some issues with some HP printer software which CCleaner cleaned, but the software in question was inside a TEMP folder so it wasn't actually CCleaner doing a wrong thing. So download it and run the temporary files cleaner part. It might find something even after running the cleanmgr (which can do a perfect job with a bunch of parametres!) The default settings are quite good although I would add browser "autocomplete" and "saved form information" to be cleaned. Then you can move over to the registry cleaning section. Run it a couple of times, usually there won't be any findings after the third run, or there's a few which won't go away. Let them be, a few don't cause slowing down. CCleaner also has a tool for startup items which you'll find quite thorough. You can either disable or remove items from there, the latter can be useful for programs you know you have uninstalled but still are trying to start at every boot.
Of course test your computer between every step!
One last thing you might want to try is a repair install. You might be familiar with it from XP, but since Vista it has changed. What you'd need is the right installation media, in your case Windows 7 32 bit. You'd also need your Windows license code which usually is on the sticker on the side panel. First make sure your computer and the installation DVD are of same Service Pack level. That means, if your computer has SP1 installed but your DVD doesn't have it, you'd either have to uninstall SP1 or get another DVD. Now start the DVD from within Windows and do an "Upgrade" install. Thorough instructions here:
http://www.sevenforums.com/tutorials/3413-repair-install.html.
Hope that helps! And just in case something goes badly wrong, you'd have your clone to continue as if nothing had happened... Actually, tweaking the clone and saving the original might be a good idea, three years is a long time for a hard disk anyway and some of your problems may be due to a slowly failing hdd.
