Computer is slow...Hardware or Software

Ok....so here is a random question. My computer has been slower then before (obviously this happens over time) But its getting to the point of leniency. For example, iPhoto takes forever to load and when you import from a Camera and begin to type in the event name, it works on a 30 second lag. Another example, iTunes takes a while to load (granted, it has 70GB worth of content). Now through all of this, ive been having weird software glitches throughout. For 2 weeks, spaces wouldnt work right. Id have to go to system pref. turn it off and on and walla, back to normal. Or just yesterday, Time Machine wouldnt backup to my external, said it was set to read only and now its fine. But key thing is, things are slow all over. From Pages to the web, to widgets coming up and you name it.

Also, ive done all the good stuff like Repair Premonitions and Disk Warrior.

So now, Im curious if its Hardware or Software.

My current specs go as this
10.5
1.6 G5
2Gb Ram
ATI 9600
160GB
500GB

External:
3 1TB HDD

So yes, I have alot of content on my computer. Heavy apps ranging from
Aperture 2
Final Cut Studios
Bento 2
CS3
iWork/Office

So again, Software...Hardware...anyway to make sure
Also to put things in perspective, where does my Machine sit in the power totum, compared to the current lineup?

Better then the base MacBook? Worse? Mac Mini eats my Machine? lol im not sure how the G5 ranks against the Core 2 Duo.

Edit:
And Time Machine is doing it again and when I click on my external, this is what it shows me and I cannot unlock it...

 

Will Do and thanks for that heads up! ill have to check into that

You know what, Aperture and iPhoto its So so on. (but to be honest, can really choke on iPhoto) but for whatever reason, Final Cut. Not a problem. Rendering takes forever, dont get me wrong but just FCP as a program and it functioning, it runs fantastic.

Of course, I say fantastic...relative to what the Machine is...lol. Ive been on the brink of getting a new unit but to frank, when I first got my Machine, I was new to the whole Mac thing. ordered it online, 2 weeks later, Dual Core 5G's came out....and then Tiger did too....

So now, 5 years later, I work for the Man and im waiting for Snow Leopard and Blu-ray before I pull the trigger as I can hold off another year i guess. (would love to pull the trigger now but cant afford to upgrade twice in a year @ $4k each time haha)

 

Yea, currently I have
1TB for Time Machine
1TB for Renders
1TB for Clips/Edits

then my internal 500GB is for Music and Photos and such
160GB original is just OS and software mainly.