My resident protection is disabled and i cant turn it on [avast home]

I’m using Avast home edition.
and i never had any problem before.
but now i started my computer and i see this icon:

http://up55.siz.co.il/up1/jejwey3bymzd.jpg

when i press to start protection it just goes back to the previous.
help?!

Welcome danielgoldman95

What is the operating system and Service Pack level you are running?

What is the CPU type and speed and how much RAM does the system have?

I’m using windows Xp sp3.
My CPU is:
AMD Athlon 64 X2 Dual Core 5600+ 3117 MHz

2GB of RAM

Commonly this relates to another AV installed or remnants, whilst you may have been using avast for a while this could take time to rear its head.

Have (or did) you another AV installed in this system, if so what was it and how did you get rid of it ?

Also check out this avast FAQ pages - AAVM subsystem detected and RPC error - Red Circle on avast icon. http://www.avast.com/eng/faq-other-questions.html#idt_1539.