scanning negatives - need advice

I've been scanning all my old negatives to dave old family photos, and
also to create a more complete portfolio for my photos. Many do not
need to be printed larger than 4x6, but some do.

I have not been happy with my scans from the negatives. I do get better
color and detail, but they don't look as nice when printed at 8x10.
This is onscreen too, not my printer.

I have checked my scanner, and it has Optical Scan Resolution 3200 x
6400 dpi. I have read the archives, and I have found many posts that
4000dpi should be good, so this ought to be fairly decent.

My guess is that I am not getting the best out of my scanner. The
driver I have gives me the option of choosing my output size and
resolution, but it does not say what it is actually scanning at. How do
I make sure I am getting the most out of it?

I have also seen some references to Digital Ice. I actually have that
program but have never used it. It came with an old digital camera.
Would this help me at all?

I know that a dedicated film scanner would be best. Unfortuinately, I
already bought one and could not get it to work with any computer in my
house (4), so I lost the money on that, and I cannot sell it, since I
cannot prove that it works. (I bought it used from somebody else).

I have several thousand frames I would like to scan, so paying a
professional place is not something I can do right now. Just too
spendy. I will probably buy a new scanner in a few months, but I
cannot afford to spend more than a $100 on one right now, and I keep
finding ones that are no better than what I already have.

My scanner is a Canon CanoScan 4200F.

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