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#41
If you're wondering whether it'll fit, open up your case and look. Take the dimensions of the card you're interested in (most important dimension is the longest one. Some list it as length, some as height) and measure. Will an X inch card fit from the back of my case to the front? If you have a drive rack or set of bays in the front of your case (like mine, all the way down the front), then measure just to that. I think with your pavilion you just have a small 2-drive cage about mid-way up the front of the case so depending on where the PCI-E slot is located on your board, you should be able to fit anything from the 56 or 57 series just fine. The 6850 I'm getting is the same size as the 5770.
A one-slot-wide card would be most ideal in your situation IF you have other PCI cards already occupying space. That 5770 was originally you listed was my original choice but I'd go with the HIS version. It's clocked a little bit higher from the start by the manufactuer and it's cheaper. Newegg.com - HIS H577FK1GD Radeon HD 5770 (Juniper XT) 1GB 128-bit GDDR5 PCI Express 2.0 x16 HDCP Ready CrossFireX Support Video Card w/ Eyefinity
^^ That's if you reeeeeally want a 2-slot card. the 1-slot that was suggested to you previously will work great as well. It just comes down to the size of the cooling apparatus. The 2-slot will vent out the back mostly, keeping your innards cooler. The 1-slot will blow every which way and probably warm up any components near it under full load.
If you search for "low-profile" specifically, you'll probably find half-height cards. These are more used for slim pcs or media center PCs and have just passive cooling (no fan). Don't consider those if you want to game decently.
And yes, a new PSU is indeed in your future no matter what. Without looking I'd say you have no more than 250 watts and it's probably already at 60% capacity if not higher. At least 650 watts as a good mid point if you want a 56 or 57 or even a 58 series Radeon card. 650 is on the lower end for the 6x series.
When PSU wattages are given in the specs, it's stating the total effective output amount. They are estimating based on hardware that card will most likely go with. I would add some on top of what they recommend. If it says 450, go 600. 500 go 650. Give yourself some room to grow. No sense in replacing a perfectly good power supply every time you add or upgrade a piece of hardware in your machine.
In regards to VGA, most discrete cards come with ONE DVI-VGA adapter if you can't do DVI. If your monitor supports it, however, you'll notice a difference if you use a DVI cable. They run cheap. I'm picking mine up from Amazon for like $8.