Here are the specs on that laptop:
http://www.pcworld.com/product/26484/gateway-m250e.html
You will be limited with what you can accomplish, but you should be able to playback music files from your hard drive. There may be some tweaks you can apply to get good quality playback:
- install Foobar 2000 as your playback software. Its free, its very customizable, and it supports direct output to your DAC (with the tweak described below).
- assuming that you still have Win XP on that laptop, you can install a program called "ASIO4All". This will help you bypass the Win XP mixer stack and output directly to your DAC. You'll need to go into Foobar's preferences menu and tell Foobar to output your music to ASIO4All. You'll also need to set up ASIO4All to output your DAC.
- Play music back directly from your hard drive at first, as opposed to (for example) an external USB drive. While your PC has 3 USB ports, you may find that your older PC struggles a bit supporting streaming to a USB DAC and accessing files from a USB drive at the same time. If you have a network attached drive, you might try streaming from your music from your network. Your computer has a wireless G receiver, which should be fine for streaming at least 16/44 content.
- If you're adventurous, you might try a version of Linux on that laptop. There are versions of Linux made specifically for older PC's that might help you get more out of that laptop. You could try the following version of Linux which is good for "beginners":
Linux Mint with the XFCE desktop:
http://www.linuxmint.com/edition.php?id=169
If you're comfortable navigating Linux, you might try something like Vortexbox. Let us know how it works out.