My internet mail scan is showing on High, and i haven't had any slowness to the pc as a sign of maybe having a virus, the pc is working at normal speed.
You won't notice any slowness bumping it up to High as for the most part it doesn't use any more resources and will be in a waiting state until you send or receive email. Having it set to high will have alerted you if your system was sending spam, so what others were suggesting you were sending spam doesn't appear correct. You haven't said what your email program is either ?
My firewall is also on, and its windows security centre
You don't say what your firewall is ?
The windows security center isn't your firewall as that is just a monitor to tell you if it is on or off.
What is your Operating System ?
Edit to add
I've just noticed that my internet mail scan is showing ( No count, but says its running?
This would bring us to your email program again and if you use webmail (e.g. view your email through your browser) ?
Or if you have to use an email program to download the email, but you have to use SSL/TLS secure encrypted email ?
What is your ISP (or where is this email coming from, gmail, Yahoo, MSN, etc.) ?