The purpose of this study is to determine whether 100mg daily aspirin versus placebo and/or supplementation with 1 gram daily omega-3 fatty acids or placebo prevents "serious vascular events" (i.e. non-fatal heart attack, non-fatal stroke or transient ischaemic attack, or death from vascular causes) in patients with diabetes who are not known to have occlusive arterial disease and to assess the effects on serious bleeding or other adverse events.