Space problems with Dell Inspirion 910

We recently purchased a Dell Inspirion 910. It has only an 8-Gb solid state
hard drive which is almost full (595Mb Free).

The problem began when I attempted to install Pinnacle Studio) which
aborted for some reason during the install and of course leaving a mess.
I would not uninstall because it was not yet registered in the add/remove
list.

The next thing that happened was that McAfee attempted an update ...
during the update I got messaged like "swap space low - adjusting" and
then the "not enough disk space.

I have removed all programs and files that I don't need or want but still
not enough space to do anything useful.

Defrag "analyze" works and says the disk needs to be defragmented but
when I click on "defrag" the system responds with "NOT ENOUGH DISK SPACE"
and the program halts.

I hate to reformat and reinstall because dell may have put some things on that are necessary but that I don't know about "YET!"

Can anyone give me some advise on how to really strip this puppy down?

Dell "t e c h support" was useless. They took over the machine and deleted one program.

I have an external 230-Gb external USB hard disk and an external DVD/DC
(lightscribe enabled) USB drive.

Any help would be appreciated ... thanks in advance!

Thanks for the response. I did both and I still have only about 600Mb free.

Yes I checked the drive space required and that free [and so did the program just prior to "click 'ok' to install". I did, IT didn't.

There are lots and I mean lots of text (file.txt) in both the windows directory
and the I386 directory. Can I delete these? (safely!?) I viewed a few of them and they seem like remnants of install scripts.

I tried Dell, one more time and they said to either get the 16Gb hard drive at a cost of nearly $200.00 or install the program on another external drive. They just couldn't understand the "not enough free space". Studio is not the problem - I installed it on another computer and it works fine.
What I need to do is get rid of some junk on the netbook. I had about 1.6Gb free before this mess. I have deleted most of the programs that Dell had installed (trials etc.) but to no avail so far. I may have to uninstall
McAfee.

Thanks again