Collecting data from multiple files accurately and easily

I'm monitoring about 40 printers for page counts on a monthly basis. I have about 3 years worth of data I'm trying to compile on 1 sheet so i can calculate things like average and deviation usage, etc. My current method for compiling this is copy and pasting individual cells which is tedious and prone to mistakes. The information on the spreadsheets is on 36 separate excel files. Each excel file has 3 columns labeled "serial#" , "BW" and "Color". The excel files have anywhere from 36-45 rows and the serial numbers sometimes change as machines are added and removed. Is their anyway to easily use this data or bring this data to a master sheet other then grinding the Ctrl+C keys?

You should be able to use VLOOKUP formulas bring data into your summary worksheet from the other worksheets, even from other closed workbooks. VLOOKUP works on closed workbooks.

Press F1 and read the Excel help files on using VLOOKUP. Once you understand the basics, it's a small step to using it between workbooks.