You cannot use the application "Install Mac OS X Lion" with this version of Mac OS X.

Well, first we need to figure out if your machine will support either OS. So, when you go to the Apple and click on about this Mac and then on more info, can you copy and paste or type the info here, like this:

(don't post your serial number).

After you post that info, we can go further,

Slateskies wrote:

... I'm doing this because of a new game that requires OS 10.6.8. ...

Why not just Upgrade to 10 6 8 which is Snow Leopard...

First you need to check that your current Mac meets the System Requirements for Snow Leopard...

Snow Leopard Specs:

http://support.apple.com/kb/SP575

If it does... then you need to Purchase and Install Snow Leopard Disc,

Mac OS X 10.6 Snow Leopard

( It should be noted that Apple will send paid MobileMe members the Mac OS X 10.6 DVD for free.)

Would Also Recommend that you do a Bootable Clone Backup of your current Hard Drive Before attempting any Major Upgrade...

By far the easiest way to make a Backup, is to use something like

SuperDuper http://www.shirt-pocket.com/

or CCC http://www.bombich.com/

Slateskies wrote:

...

Memory: 2 GB

@Ana Music: I went for Lion first because I have a sibling who says "Well if you're gonna upgrade, why not upgrade all the way?" Listening to him may have been a mistake. :/

😁

If you decide on SL then would recommend increasing your RAM = Memory to at least 4GB.

http://www.macsales.com/

As for Disk Space... Open Activity Monitor > Disk Usage

I agree - increasing RAM always has a positive result. As for Lion, well that is your decision. One thing to consider is the fact that if you have older PPC apps, they will no longer run under Lion because Rosetta hs been discontinued. Snow Leopard is the last OS you'd be able to use them with.

Slateskies wrote:

...

1. Is RAM something that a computer layman like me can install? ...

Absolutely... See Here...

Installing RAM

Desktop http://support.apple.com/kb/ht1423

Slateskies wrote:

...

2. Would Adobe CS3 stuff be among those older apps that Lion would defunct?

See Here to Check the Compatibility of Third Party Applications you may be using...

http://roaringapps.com/apps:table

RAM is easy to install - OWC have how to videos on their site (and it's also in your user manual as well as the Apple support site):

http://eshop.macsales.com/installvideos/imac_mid_2007/

And here is the page for your model's RAM:

http://eshop.macsales.com/shop/apple/memory/iMac/Intel_Core_2_Duo

According to the table on this site, your Adobe stuff should be ok, but better to check with Adobe support first to make sure:

http://roaringapps.com/apps:table

Edit: @ AnaMusic: well, at least we're on the same page - when I hit reply, there was no other reply showing....and since the question was directed to me, I figured I'll leave my reply rather than deleting it.