Should be ok. Just make sure the back I/O faceplate is removable from your current system. I suppose it's not *really* necessary, but it does help keep dust and critters out of your system. Additionally, you'll want to take into consideration how the front connectors (Power, Reset, HD Activity) of your current PC connect to the motherboard.
After all that, the graphics card idroid suggests is sufficient for your HTPC needs.
Don't know why you think you need a NIC as your current system already has one onboard.
I noticed that after I made the post (was hoping no one else would). This PC has been sitting in a closet for years, I didn't look at it closely until today when I found out this htpc transformation was possible.
Just realized this video card requires a 400w power supply but my case came with a 300w supply... Am I screwed? I can't imagine this card reall draws more than 100w so why require 400?
Side note, my motherboard has a digital audio out. Is there anyway to convert that to an optical input? Do they make cables like that? I'm not finding anything online. If not, can I convert digital audio into a 3.55mm jack? 3.55 and optical audio are the only inputs on my tv.
The only things in this HTPC are an HDD, DVD drive, and a video card. You really think 300w wont cut it? I'm seeing tech reviews saying this card draws 16 watts.
Another side note... I just pulled out the motherboard and there was a black cover that said "Do not remove" on the I/O covering up onboard audio ports. Why would they do that? There was an audigy sound card in a PCI slot.
Since the graphics card does not have an external power connector, it can only draw power from the PCI-Ex16 slot, which maxes out at 75 watts. Given that it's such a low end card, I can't see it ever drawing that much power. You should be fine with the *cough* proprietary *cough* 300 watt PSU.
As for the on-board audio ports, they should work just fine. The manufacturer, most likely, just covered up those ports so users would be tempted to use them over the PCI sound card that was installed.
Why do you think they installed the pci card to begin with?
Btw, I finished moving the old comp to the new htpc case and I haven't been able to get the audio to play through those jacks yet. I'm sure it's some kind of driver issue but I haven't figured it out yet.
I was thinking is was some sort of marketing gimmick from back when sound cards were awesome. Check BIOS to see if there is a setting to enable on-board sound. Otherwise find out what chipset is used for audio and find the drivers for that.