Is this a work or home PC?
Do you know anyone called Marc who may have logged on to your PC at some point, either directly or using Remote Desktop?
AFAIK, the only way a true roaming profile can be created is with a domain user account* - is your PC a member of a domain?
If the answers are: home, no and no, then malware jumps to the top of the list of suspects.
SD
* There is a kludge to get pseudo-roaming profiles to work in workgroups, but it's not officially recognised my MS - and I think you'd know if you had implemented it!