Dell Vostro 410 Power Supply upgrade. Help?

Hello, I've worked in the summer break just to earn some money from which I could upgrade my graphics card (Gigabyte's GTX460 1GB) for which I need to upgrade my PSU.

It comes down to this: I'm confused. I have found people on the internet that say that the power supply is propriety or something so I can't change it.
Other people said that it would be no problem to put a normal ATX PS in it because they stopped doing propriety Power supplies in the Pentium III days.

Now, what should I believe? I opened my case to find out that some weird metal things in my case hold the PS in place or something. Like 2 little 'hills' or something. The size up to those 'hills' (don't know what to call it) is 140 mm with a height of 85mm. Now, not looking at those hills it could be 150mm (which nearly all power supplies are!)

The mobo is a Foxconn DG33A01. With a 24pin connector.

If you know anything about this, please help me out. I'm worried now. When I bought this PC 2 years ago it said that it was good for later upgrades.

So, yeah. Please help!

Pretty much any standard ATX power supply will work.
Act quick and you can still catch the deal on this
http://www.newegg.com/Product/Prod [...] 6817139004

Okay but what about the sizes? any power supply nowadays are like 150mm long, and I think there's only space for 140mm? There's loads of space after those 2 metal 'bumps' I mentioned. Should I simply get a saw and chop it off? Or what? xD

I don't know, I'm afraid of taking risks

i've tried many times to fry different dell psu's.
i mean totally abuse them to see exactly what they can handle.
as far as I'm concerned, they're under-rated and by your explanation,
" Dell power supplies are not under-rated, that's a notion that came about due to them being rated properly, by max continuous output, not peak output like many generic psu's. "
to some people they can construe that we're basically saying the same thing in different ways.
fellow dell guy.!

'bumps' will not be an issue as - delluser1 states.

Ty =)