The awareness of the importance of effective health information systems (HIS) has increased substantially and is reflected by many ongoing efforts of HISs reform in many developing countries. However, the one mostly mentioned obstacle for health information systems reform is Legacy Information Systems (LIS). The impacts of LIS in the reporting of routine health delivery services were studied in a participatory action research using case study sites in Tanzania and Mozambique. LIS impacts are on the process of introducing changes (reforms) on the HIS, and on everyday functioning of the HIS. LIS were determined to cause poor quality of health data, incomplete reporting of health data, and burden to health workers. The study recommends the Ministries of Health to relinquish the LIS. A demonstration on extracting and loading of locked health data on LIS to new health information software using extraction transformation and loading (ETL) software was performed.