Factory Reset - Is startup disc needed?

Hey,

So it appears that I have encountered a virus on my 2009 macbook. Weird ads keep popping up in google chrome and safari no longer opens.

My motherboard needs to be replaced as the headphone jack is not functioning and my disc drive is non responsive with a disc trapped inside.

I realize it is an older model, but it still functions fairly well. In the fall a new hard drive was installed as the computer became incredibly slow. I was running Snow Leopard at the time. I took it in to a licensed repair guy and he installed the new hard drive and updated me with Lion however my computer has been slower since specifically Safari. Hence downloads of Chrome and Firefox.

Anyways to deal with the virus I am wanting to backup my hard drive, and reset to factory settings, however with a broken disc drive I am wondering whether or not I need a startup disc.

Thanks.