SKTools was updated to work with WM5. It's also a tremendous app, but a very powerful one. It has many uses and features, but it's not too easy to navigate unless you're pretty comfortable under the hood of your PPC.
http://www.pocketgear.com/software_detail.asp?id=14288
A more user-friendly memory utility app would be Dinarsoft's MemMaid.
http://www.pocketgear.com/software_detail.asp?id=14279
I own both and use both regularly. I've learned to be careful with SKTools after removing things I shouldn't have removed.
I would recommend that you have one of these types of programs to keep unwanted junk off of your machine and to gain easier access to some customization features of your device.