I have the steam version of vice city installed on my laptop and pc. On the laptop the infinite sprint glitch works just fine, no worries. I tried two different keyboards on my pc, but it does not work as well as on my laptop. It seems that I have to hold down the sprint button for a short while before tapping it. If I tap right away on pc, tommy will not start to sprint. The keyboard settings are the same on my laptop and pc. What could be the problem here?

Dunno what could cause that, but I do the same thing as you noticed, I hold Shift for a short while and then start tapping.