You can get your sound in various ways and continue to use the speaker system. I am assuming that 2.1 system uses 3.5mm stereo plugs. No doubt about it, I would think.
If you have a graphics card, you can port sound through HDMI to an AVR with HDMI inputs. You can also acquire a decoder device with 3.5mm outputs (in addition to optical, HDMI -- possibly RCA) and HDMI input. I personally had one in mind for myself, but it's been a few years since I looked into it and I can't remember the name or model. Lemme think a-minute:
HDMI LPCM 7.1 5.1 Multi-channel Decoder $58 bucks (!!!!-and-read-on)
This is the same device, maybe renamed, presented in the identical way as the unit I saw three years ago. At that time, they occupied a price-point of ~$130 to ~$140.
Let me say that I dabble in computer-sound apps and options. I am not that knowledgeable. But there are many good analog computer sound systems: Mine is an old Logitech Z7xx (I can't remember the model-code, and the labels aren't immediately accessible) 5.1 system. I can switch one computer between the Logitech and an ONKYO 7.1 AVR, but the Logitech seems to be getting 300 out of 365-day usage.
Anybody who thinks this is not the device I myself am assuming it to be should speak up -- especially -- because the price-point is such that I will spring for it myself. And I wouldn't want to mislead the OP.
Just as afterthought, there are ~$25 HDMI splitters you could combine with this particular model -- I just have yet to try it myself. I happen to have such a splitter, so the impulse-buy is almost a dead certainty unless I'm barking up the wrong tree and somebody gives me a heads up.
UPDATE: Yes, I have conviction this is the device with features I assumed it has. It is also HDCP compliant. Some of these devices -- I found one sold in Australia of a different make -- are priced at $160 or so. I think I found one alternative running between $500 and $600. But if it works and works well . . . I have to tell . . . I just pulled the checkout string from an EBay outfit with 13 to sell.