How to recover Lotus Notes client?

There was lotus notes 7.0 on my PC. I install it to enjoy Designer from Lotus 6.5.3. I’ve decided not to install old version. But suddenly my Lotus 7.0 has been removed(uninstalled) . Then I’ve made system recovery before this changes. But client is still doesn’t want to work and says Cannot write or create file. We don’t have a Lotus admin in our office. But I’ve got distributives of 6.5.3.
I’de like to know how to recover my client without big problems. What is necessary for it? On my neighbors PC is working version.