I have downloaded Limewire 5.4 but every time I close limewire and open it back up, it reverts back to 4.18 and asks me to update to 5.4

Why does it do this and can I make it keep the 5.4 after I download it?

Sounds like the LW 4.18 version still exists on the computer. The LW 5 installer should have uninstalled LW 4 as it was installing.

Do you know how to navigate to the Programs folder? If yes, go to this folder & find the LW 4.18 folder & open it. Inside the folder should be an uninstaller which can be opened.

I had previously uninstalled limewire from my system using control panel add/remove programs. I found my limewire folder, but it only contains 5.4...

ah ok .. I had wondered. Using the Add/Remove Control panel is not the way you should uninstall LW. Normally it should be via the Start menu -> All Programs -> LW -> Uninstall.

Try this technique but ignore the reinstallation of Java: http://www.gnutellaforums.com/333278-post2.html ie: ignore steps 1, 4, 6 & 9.

To maintain your incomplete downloads history, you will need to keep a copy of your downloads.dat file from your LW preferences folder, though deleting the preferences folder 'might' not be needed anyway. Try the other steps first.

I like the spelling of your name btw.

So i have downloaded the offline version, uninstalled limwire using start --> programs and the entire limewire folder is gone. It said it was only uninstalling 5.4 though.... does that matter?

Did you run CCleaner (set to registry) after uninstalling LW before reinstalling LW 5?
If yes, give it a whirl by opening LW & see what happens.

There is somewhere on the LW website that suggests uninstalling via the Add/Remove CP, this is incorrect advice (sighs) & creates a new problem & many people end up coming here seeking advice how to fix their issue.

I'm downloading ccleaner now

I did all that and it still opened back up limewire 4.18....

Search your computer for limewire. See what results you get. See if there is any other program listed other than LW 5. You might need to go to the program file's details window to seek information about it.

You should certainly know if LW 5 is opening because it looks totally different to LW 4.

You could possibly try rebooting & repeating the process without opening LW until the final step. Perhaps elements of LW 4 are still stuck in memory or haven't completely closed whilst you are attempting to uninstall & reinstall. Also, this time, delete the LW preferences folder before doing this process.

I am highly surprised CCleaner did not pick up on the issue. CC is usually highly reliable for finding these kinds of issues 'if' there are older elements of programs still lingering on the system.

After installing LW 5, you will need to re-add it to your firewall exceptions.

Try delete LW's preferences folder when LW's properly closed. See point 3 here & also point 2 if you've used very old versions of LW in the past (there could be a folder in either location).
Fixes for LimeWire

This will change all of your settings within tools > options, you'll have to go back through afterwards & reset things. If you're not sure of your settings, go through LW's tools > options & write them all down, so that you can reset things later.
Vista users: LimeWire Pref Folder in Vista