Is there upsampling software?

[dbbd]

My HTPC is connected to my LCD through analog VGA cable.
Is there software that can run on the HTPC to upsample AVIs in order to
get improved video quality?

Does the question make sense at all given the analog vga connection?

[redwudz]

You can set a different screen resolution in your computer graphic card display settings, but your LCD display will probably do a better job of upsampling. What LCD display, brand and model, do you have or what is it's native resolution? What is your VGA setting (Resolution, refresh rate) for the video that is sent to the LCD display?

[dbbd]

I have an LG LC42R LCD TV, and the
video card is (no laughs) nvidia mx440.
I think the resolution is set to 1440x900,
but I'll need to verify that.

[Krispy Kritter]

That TV has a native resolution of 1366x768. So any resolution (higher/lower) is converted by the TV to it's native resolution. In your case, your input resolution is actually being downconverted. There is no need to upconvert or increase your resolution. You may try setting your desktop resolution to 1366x768 and see if it gets any better (or worse).