I think there's several possible methods to help you clean up your system, and may depend on exactly what you need to do.
What do you need to do (what concerns you the most right now?)
Can you tell me what you mean by "clean up"?
What is your goal with an upgrade? (how far do you want to go with that?)
Do you want to upgrade to a newer Mac, or simply upgrade what you have now as much as possible?
And, to answer that - let me know what Mac you have now, along with how much RAM memory is installed, and how much free space you have on your hard drive.
I have a imac intel. It is running really slow. I am guessing I have duplicate files slowing things down. That is the clean up. Upgrade is to get a little more upgrades out there I was thinking getting to 10.5
My computer is imac 5,1 intel core 2 duo, 2 ghz, memory 1 gb, 667mhz ddr2 sdram
I think it's not too likely that a few duplicate files would be affecting the performance of your iMac.
"Really slow" can be caused by several possibilities:
1. A hard drive that's nearly full - check that you have plenty of free space, at least 10% free of the total available The smallest hard drive in your iMac was 160 GB, so on that one, more than 16 GB free space is reasonable.
2. Using software that is using more memory than you have installed, causing lots of page outs to the hard drive. That will slow your system down dramatically. When you get a slowdown, open your Activity Monitor (in your Applications/Utilities folder), and make sure the drop down menu is set to show your "All Processes", and not just "My Processes". You can sort the list of processes, by clicking on the header for % CPU, for example, to show the highest CPU use, by process. Click in the bottom window for the CPU window, which will show graphically, how much total CPU activity you have at the moment. Click on the System Memory tab, and notice the amount listed by Free, and Page Outs.
3. If neither 1, nor 2 show you anything way out of normal, then you might be at the OTHER common problem with a 5 or 6 year-old Mac - a possible failing hard drive.
1. you can help by clearing out old files, or apps that you don't use.
2. Lots of activity that are related to high Page Outs might be improved by upgrading your RAM. 1GB is not very much, especially on an Intel Mac. Your iMac Core 2 Duo can be upgraded to 3 GB maximum RAM. If you upgrade your OS X system, you would definitely want to do that memory upgrade.
3. As your system gets older, your hard drive is more likely to fail. It's not too simple to replace, but is do-able.
One test that you CAN do, is to boot to your OS X installer DVD, and run Disk Utility from the menus. Don't waste your time running Repair Disk Permissions. Your goal is to see that Repair Disk passes with no reported problems.
4. If you have plenty of free space on the hard drive, and you can upgrade your RAM to a larger amount, Then I suggest that you bypass 10.5 completely, and upgrade to 10.6
Several reasons for that:
10.5 is still high priced, and not always easy to find now. You can purchase 10.6 directly from Apple, for only $20 http://store.apple.com/us/product/MC573/mac-os-x-106-snow-leopard
Snow Leopard would be a fine upgrade for you, as it's quite stable, and your iMac will run it very nicely. You COULD then go to Lion, but you won't have the advantage that newer Macs have with more RAM installed - and too many folks here will tell you that Lion is a much bigger leap, than going from your Tiger system to Snow Leopard.
Just my opinion...
You have two RAM memory slots.
You can see how those are installed now, through your System Profiler.
Most Macs come with a card in each slot. If you have 1GB total, then likely it's two 512MB cards.
You can replace each card with more. Each slot can take up to 2 GB PC2-5300 SO-DIMM
So, you could install one pair of 2GB cards, to give you a total of 4GB, but only 3GB will be used by the system.
There's good reason to install the pair, as you would expect (slightly) higher performance from a matched pair.
That slight speed increase may or may not be noticeable to you.
Another reason is that you can sometimes find pairs for sale at a small discount
Otherwise - 1GB in one slot, 2GB in the other slot to get max memory.
Looking at your other thread - yes, 10.4.11 will still be fine, but you could upgrade to 10.5, or 10.6, or even to 10.7 - although best results would be with 10.6 (again - my opinion.) 10.6 is much easier to find - you can get directly from Apple, and only $20.
And, of course, you would still need to upgrade your RAM, if you have not done that yet. There's even some advantage to installing a pair of 2GB RAM chips. That may give a (slight) performance increase because of a matched pair - even though all of the memory would not be recognized.