Hi,
first of all, that's not really much (resource I mean). Please also note that extensive Excel spreadsheets, which I presume are all linked to each-other (meaning they use data) and contain complicated formulas and conditions, make Excel in it's essence slower. It's may not be that your computer is slow, but the program cannot handle the data any faster. Analyizing and calculating is a lot of work
Hope to have helped.
Rgrds,
Kristiina