How did you get the video into the PC?
Firewire is a common method but you may be able to use either S-Video, phono connectors or USB.
Once onto the PC the file will be an AVI file. This needs to be encoded using TEMPGEnc (or similar) which produces two folders: AUDIO_TS & VIDEO_TS. Within these folders are VOB files.
Using DVD writing software, drag the VIDEO_TS contents into the VIDEO_TS folder in the burning programme - do NOT delete the AUDIO_TS folder (evenn though its empty) as your DVD player looks for this folder before looking for the VIDEO_TS folder....if it can't find it then it won't play.
So, in answer to your question, if you have sucessfully copied the video to the HDD then you will have an AVI file - that is all you need to begin the process.
Sorry if its a bit long winded - thats the joys (?) of DVD writing.