Took my bicycle to LBS yesterday. A slight adjustment to the front derailleur was all that was needed. Chain rings are okay. LBS informed me that what I thought were worn chainring teath were part of the IG drive system. Was also told that HG is compatable with my bicycle as long as the HG is for a 7/8 speed. LBS mechanic also took my bike for test ride after he adjusted front derailleur. I'm good for at least 1500 miles. I should be able to get 2-3 cassettes per chain. Also when my bicycle was made Shimano had just introduced the IG system. The "USE IG CHAIN ONLY" was to prevent somone from installing a regular chain onto bicycle. I went for my bike ride this morning and evrything is shifting fine.