The hardware limit is 1200x2400 dpi. VueScan can drive it to 4800 dpi through interpolation, but that results in massive 500MB+ files with no real detail gain. Stick to 1200 dpi for film, 300-600 dpi for documents.
Choose and look for a generic "USB Scanner Device" if the specific UMAX driver doesn't appear. umax astra 5800 scanner driver for windows 7 64 bit best
VueScan by Hamrick Software is a universal scanning application that includes its own built-in drivers. The hardware limit is 1200x2400 dpi
VueScan includes reverse-engineered drivers for over 57 UMAX scanners, meaning you don't need the original UMAX driver at all. umax astra 5800 scanner driver for windows 7 64 bit best
Some driver repositories offer WIA-compatible drivers specifically for the Astra 5800 on 64-bit systems.