Remote Desktop and How to see if someone is on your Wireless?

Could anyone please give me any free good remote desktops that I could use to access my home desktop while I am at work?

I use a iMac at work but have a Dell at home (go figure) but I wanna be able to access my computer from home if need be or just to check some things out like if something finished downloading or moving a file I may need at home on my computer from anywhere I maybe.

Its not that important that's why I dont wanna pay for anything but I have used orb and that was extremely slow.


Also, is there any software I could use to find out who is accessing my wireless network if any or what someone is doing on my network with per say a wireless laptop.

I have a Belkin Wireless G router