What is the difference between these two adapters??

Neither is an OEM Dell adapter - they're third-party units.  As long as you realize they'll power the system but WILL NOT charge the battery, either should work.  If you need an adapter that will charge the battery and power the system,  get a genuine, OEM Dell adapter -not a third-party unit.

Really? Because the HA9 one is the adapter that came with the laptop when I bought it directly from Dell and has the Dell logo on it.

The FA9 one also has the Dell logo on it.

- I believe they are both actual Dell adapters, considering the first one came with the machine.

- My main point is I want to know if the FA9 adapter will work without any hiccups. Or better yet if anyone knows what the difference between the HA9 and FA9 models.

~~~I've also used third party units, and besides being extremely breakable (the latest of which literally melted and gave me a 2nd degree burn) but they are used as replacements and DO charge the battery and gives me full CPU power as well.~~~~

Nyump~

I would not recommend EITHER for a 17 inch Laptop but rather a 130W PA-13 PA-4E or better PA-15 150W adapter. P/N: PA-15, 310-4180, 310-6580, 310-7848, 310-7849, 310-8275, 310-8537, 320-2746, 330-1829, 330-1830, 9Y819, D1078, D1404, D232H, D2746, FC892, K5294, N3834, N3838, PA-1131-02D, PA-1151-06D, PA-1151-06D2, PH298, TC887, TC912, W1828, W7758, X408G, X7329, X9366,ADP-150EB, AP11

The correct answer to your question is:

Model: PA-3E FA90PE1-00

Power provided: 90W

Output: 19.5V 4.62A

HA90PE1-00  PA-10

Power provided: 90W

Output: 19.5V 4.62A

Difference is the Power cord and the Model Designator.  PA10 vs PA3E  The 3E is flat and has a blue Ring on the dc output end thats the pilot light.  The PA10 has Green LED on the Brick.

HA90PE1-00 (PA10) has a FLAT 3 prong cord.  Flat hammerhead Power Cord  (These are not easy to find)

FA90PE1-00 (PA3E) has a Mikey Mouse 3 prong cord.

There are "clone" adapters with the same part numbers on them (presumably to fool people into believing they're OEM Dell).  That said, for a 17" notebook with an i5 or lower CPU and integrated video, 90W is fine.  For an i7 or with discrete video, you really do need a 130 or 150W adapter.

The difference is likely that the two adapters were built by two different suppliers -- Dell uses many different component suppliers, and even if the "family" is the same, the part may not be.  Sometimes the manufacturer's name is on the adapter - Delta, Liteon, etc.  

Well this 'answer' was just as baffling and confusing as the rest I've been getting...

First off - like I mentioned before the HA9 came with the Dell laptop when I bought it, directly from Dell.

Secondly, I am not an idiot... when I say I am looking at them both and they both say the exact same expect for the model number, I mean exactly that.

THEY BOTH say PA-3E family!!!!

And the HA9 one has a "mickey mouse" style plug area. So when you say it had a 'hammerhead' style - XD

Ya I did find that earlier in a PDF I found on the site.

Flextronic - FA9

Hipro - HA9

The machine is getting really old so

CPU - Intel Core 2 Duo (T6500)

Graphics - ATI Mobility Radeon HD 3650

So i5? i7?  HA!  lol

And when you said - "There are "clone" adapters with the same part numbers on them"

were you talking about those photos Speed Step posted or something I said?

When you search for those part numbers, a host of clone adapters that have the same alphanumeric sequence in them show up - which isn't that surprising.  

The clonemakers make it as tough as possible to determine OEM from third party.  

Effectively the two adapters are just of the same spec, from different manufacturers.