Hi I am mostly a gamer but recently when Battlefield bad company came out I started having problems running the games, I have to turn down all the graphics and in maps with lot of particles it is slow. My question is : can my pc be upgraded to get that kind of game running. I was thinking about the videocard at first, tell me what you think.
I think you're looking at a new build. Everything in there is pretty old is really isn't going to be useful for an upgrade.
Depending on your monitor, you could easily have a new build that'd be good for gaming for under $700, possibly lower as this includes the cost of a HDD, PSU, case, OS and optical. If those components are reusable, the cost could be as low as $400. I'd suggest that you take a look at the guidelines (the link's in my signature) and see what kind of build we come up with. Don't forget to include the exact parts that you already have, especially the PSU.
Try pricing out a X3 440, Gigabyte GA-790XTA-UD4, G.Skill Ripjaws 2x2 GB 1600 mhz CAS Latency 7 and HD 5770. That's about $450 US, so it's likely to be about $500 CAD. That'll give you a build with some decent power and a great upgrade path.
I should point out is that an easy way to save some money is if you don't think you'll ever add a second card in Crossfire. Crossfire is generally a good way to create a cheap upgrade path down the road, but it may not be necessary.
If you don't want to be able to add a second card, you can switch the motherboard to a Gigabyte GA-770TA-UD3 and get a 450-550W PSU. You should save around $50 with those changes, possibly more.
Not really. You could use any two Crossfire enabled cards, but it would default to the weaker one, so you'd essentially lose some power. It's better if you use the same card. It definitely doesn't have to be the same brand though.
If you're asking because you want to use that older card with a 5770, that won't work. They're entirely different chipsets and wouldn't be compatible in the slightest.