I want to Upgrade my Dell vostro 220 PC

Dear All, Hi, keep the good solutions coming!

I have a question for you. Its regarding my Dell Vostro 220n PC. I want to upgrade it...

It has a 350-watt power supply and a PCI-express Slot (type 1.0 , 2.0 or 3.0 i dont know..) for adding a graphics card...
It already has a built-in 1024MB (1GB) video memory...

I am sort of new to the graphics cards and gaming industry...

Please can you advise me as to which would be the best choice for a graphics card for my ususal HD video editing / converting and viewing
and also I am a casual gamer like Need for Speed Undercover, Tomb Raider Underworld, EA Sports Cricket 2007 and Fifa 2010.

Hope you can help me select and buy a Graphics Card for my PC..

and I almost forgot...
my PC has a 2.50GHz Dual-Core E5200 processor and I have 2048MB (2GB) RAM.
My system is 32-bit now and it is written 64-bit ready... I am currently running Windows XP SP3 but can i upgrade it to Windows 7 Ultimate 64-bit or i have to use 32-bit ver?

I am also planning to upgrade the Power Supply as required and i will add more DDR2 Ram if required...

Can I also upgrade my processor i have a LGA775 Socket on a Dell 0P301D Motherboard?


I think this info is enough for you to help me decide the best possible graphics solution for me...

hope to hear from you soon...

please do reply as this is my first e-mail to you...

can you also please send me your web links, youtube channel, blog, etc.

bye---
Mohammad.