Hi friends,whenever you're gonna install sum interesting and important software,its shown "certificate error,expired or file corrupted". To get rid of thisproblem you have to hack your phone's system. Bt haking a phone has many ways, and depending on handset m0del hacking differs.Trying a lot,using many trix i failled to do it on my phone.bt at last in a simple way i hacked my m0bile.i found it 100% working with the pre fp1 , fp1 and fp2 handsets.you dnt need any certificate or key, coz im gonna provide you signed softwares.so lets start 1.First download the these softwarefrom bellow link >>Norton symbian Hack.sisx >>X_plore (skip it if you alrdy haveone) >>Rom patcher plus 3.1 2.Now install Norton symbian hack.sisx on your phone, and start it 3.Go to "Option">"Antivirus">"Quarantine list" and select it 4. Then select "restore" from option and click "yes" as 5.Now go to your application manager ...