when im using my downloader and downloading files, my internet speed goes up and down it even stops. It usually stops every 20 seconds and then takes 30 to come back. i dont know how to fix it. it all started after i installed an anti-virus program

This is probably because you donwload large ZIP or RAR files that your antivirus program first needs to unzip and then check for viruses when the file is written to disk. This may take some time with older systems and certainly depends on the size of the download Deli PS : this is an exchange server forum