How much does a domain's age affect its ranking?

[prodavachi]

JZ from Ohio asks:

"How much weight does the number of years a domain is registered for have on your ranking?"

[Google Webmaster Help]

Can a purchased domain's history affect its trust in Google?

I bought a domain 7 months ago. The website I put on it still doesn't show in the SERPs. Since 2000 it's had different owners - used by a co. in Oz, it's then served ads, then "for sale" with a company for 4ish years. Will it have trust issues in Google?

Dave Shuts, Yorkshire, England