I checked out the prices and noticed there was a button saying free for Citrio users. Citrio is a new browser similar to Chrome.
I did not want to install Citrio as I have read a few bad reviews about it so I had a think on how I could use it. I then remembered I still had VMware installed with a Windows 7 PC ready to roll.
I fired it up, downloaded Citrio and installed it. I followed the instructions about adding a link into the address bar and hey presto, my account was changed to premium.
I can not use 4shared on my real PC unless I convert it back to a free account.
For the mean time I can use premium features on my virtual Windows 7 and not worry about any nasty stuff that might be lurking around caused by Citrio. When I have finished uploading all the folders that I need to add, I'll then convert my account back to free and carry on using 4shared in Firefox on my real PC.
If anyone finds this useful, leave a comment :)