The only way to put files onto the 5045 from a PC is to either
a) Burn them in DVD format onto a DVD and then copy them onto the HDD of the 5045
b) Connect the laptop upto the 5045 using a TV output on the laptop and then record them onto the 5045 in real time.
c) some people have had success using the firewire port and using the same realtime copy as B but using firewire. Its very slow to assemble the video though. My 3GHz laptop was running at 0.4x speed to assemble the file before it sent it via firewire to my old Philips DVDR. Think the liteon is fussy though with its firewire port.
If memory serves me right, the 5045 can playback MP3 files that are on DVD or CD so you just need to burn them to a disc and put them into the 5045.