Absolutely no personal experience of Vista, so my comments depend on XP Pro experience.
I don't think your problem is related to PSU issues.
If the PSU is overworked, (unusual) then other more primitive things would happen, like sudden shutdown or freezing.
Vista Ultimate probably includes software which by-passes the need for other software like Nero.
So either the DVD writer is wrongly configured or perhaps the drive itself needs a firmware upgdate.
If these suggestions solve nothing, then I'm sorry, but you did ask and it will bring your thread up again.