What about the case? if you are getting a new case then I suggest you get an Antec Fusion case, which includes remote control and software. You can control the unit with a remote control.
Whether you want a Blue-Ray Player DVD Burner Combo or Blue Ray Burner. I recommend Pioneer, they make reliable drives. Make sure you use it, with CyberLink PowerDVD 9, it offers the best HD, Blu-ray and DVD playback and for burning medias use Nero.
As for memory 2GB is ok, with prices near record low, I think you should add another $20 and opt for 2 x 2GB, this will make your new system more future proof.
You could also get a wire less keyboard and mouse for browsing the net (logitech is popular,). You can download HD CLIPS, movies. And of course to access the net you will need either a pci wireless N adapter or USB wireless N adapter. Netgear is a popular make, is best to go with known brand else might get into compatibility issues with windows 7.
Also consider adding a Bluetooth to your system either by adding a Bluetooth pci card or A Micro USB adapter. This will allow you to wirelessly connect your Bluetooth devices such phones, music player to the system.
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