What I'm seeing is SP mode with mono audio, and you say it has good color and no historical issue tracking in other machines. That's outstanding.
The biggest problem with VHS was chroma noise. That's a red/blue misty looking noise that interrupts color. It's easiest seen on a black/dark or red solid image on-screen. The way to remove this is by using a DVD recorder with a built-in chroma reduction circuit (LSI Logic chipsets), or by use of an S-VHS or D-VHS VCR with a line timebase corrector (TBC). So replacing your VCR for about $200-300 might be a consideration, of quality is really of utmost importance. It is to me, so I own a trio of S-VHS machines like this.
A standalone TBC may or may not be needed. It depends entirely on the signal integrity of the tapes (not a visual issue, but a signal-based one). It also depends on the nature of the digital recording device, and how strictly it attempts to interpret anti-copy false errors.
If color and clarity needs no tweaking, then no proc amp or detailer is suggested or would be needed.
Your computer is probably fine. It has the horsepower to deal with most files. The only glut might be Vista and its piggy nature. Or the PCIe graphics interface, or a lack of PCI cards if one exists. Nothing to worry about until there is something to worry about. Computer seems okay so far.
You'll need new software. Luckily, some of it is free or super-cheap.
Less than $1,000 is no problem.
By joining this forum, you'll have no issue picking this up in 1-2 months. Free forums would have been unfiltered/overkill information that would likely cause more confusion than not. Going it alone would have required months, years, of reading. I'll fast track you past all that mess.
On to the questions and information...
1. What is the model of that Presidian DVD recorder? It might be a LiteOn clone that uses an LSI chipset.
2. If you're open to buying a good VCR, should one be needed, I can start to hunt down a deal for you.
3. You will not be needing Sonic DigitalMedia LE. Instead, go download the free (and better for video) ImgBurn
4. You will not need Windows Movie Maker. You will not need Roxio. Better software will be suggested as we proceed. It will yield higher quality and have less errors than those two basic freebie-quality apps.
5. I assume you have some Digital8 tapes to transfer? If so, that will take another method, different from VHS tapes. I can help on that too, just let me know that there are D8 tapes to be done.
I think that's it for now. Answer those, and I'll get back to you.