Windows 95 very slow

I have a client that I installed an HP External 5 Gig tape backup system on a Compaq Deskpro machine. I then did a full backup with no problems. Backup finished and I ask the client to click on the icon to bring up the backup screen and for some reason the icon would not run. The system no runs very very slow. If you click on the start option it may take 1 minute to bring up the start options and another 1 minute to get to programs.
If I boot up in Safe Mode it runs normally with good speed. I have removed all of the HP Colorado backup files and disconnected the unit. It appears that some .dll has become corrupted.
Any ideas will be sincerely appreciated.
TIA
Robert Payne