I have just downloaded both the .exe and .7z file for the Fireworks CS4 trial. I downloaded the files using Firefox 3.5 on Windows XP. When I hit launch in Akamai, nothing happens. If I double click the .exe file in Windows Explorer, the command propmt opens and then quickly shuts and nothing else happens. I have 7-zip and Winzip and neither can extract the files from the .7z.
I'm not 100% certain I have administrator rights on this computer, but I routinely install and update software and it has never been a problem in the past.
If you cannot extract the files, maybe the download did not went well, and file was only partially downloaded? Maybe you shoud try to download it again?
You also must have administrator rights to install software on your machine, no matter if you use XP or Vista/7.