I have Windows 7 build 7100 and have successfuly installed Outlook 2007, and transfered data files over from OUtlook 2003. Using multilple email address each with own data file, sending and recieving normally until trying to send large files (pdf files of 5MB or greater). Smaller files send ok (3MB sent fine). USing cable modem thru Bigpond, all ok, spend 2 days on phone checking system and had tech in to look, 'Bigpond' say not them. I can send the large file via Webmail, so maybe.... Have ample file strorage space (850GB free) and .pst files max 1MB, most 500KB. Microsoft tech line 'cant' help as using eval copy of windows 7. Any other 7 users have this issue? Or a solution?