Using image formats in Word (Word XP)

I am trying to standardise image formats used in my workplace with the MS Word document. Currently there are various iamge formats have been using eg, BMP, JPG, PNG, GIF and once the document become too big (30 -50 pages) with a lot of iamges in it, the document quit offen lost its formatting, the file size of document is also become big. Some people has suggested that we should use whatever the applications and output the iamge as EMF or WMF file format, then insert it into word documents. Any suggestions?