almost five years i got a loan from a bank. it was for $1500. i was young and stupid. never paid it back.
i have gone through alot of personal growth since then. currently i am a full time student and i work full time managing the finances of a company (thats the ironic part!) and im only 24.
anyways here's what i learned:

the particular bank i received the loan from never reported the debt to collections.
instead they merely wrote it off and closed the account. the last time they reported it to any credit bureau was over 4 years ago.
currently the debt is not being reported so it's not affecting my credit score (which i have raised to 720 and rising!) its merely showing up on my credit report.
now if i were to re-pay the debt and establish contact with this bank they would start reporting this debt again and it would start affecting my credit again.
but if i do nothing it will be off my credit report in 3-6 years. (items stay on your credit report for 7-10 years)
so in my case it was better to let sleeping dogs lie. i think this only applies to amounts under $2000.
but something for you to look into if you're in a similar situation......