1 question and 1 problem

I have tried to use Zoho Show to do a web presentation of a Powerpoint presentation on my Desktop to a participant. Unfortunately when I click on the presentation to move from slide to slide, the participant tells me that the slide takes quite a bit of time to change on their end...maybe 10 to 15 seconds after I have clicked to change the slide. We are both on Cable modem (not DSL). I'm on Firefox using XP Pro.
I've noted that in the past others have experienced this same slowness. Will this be improved? Unfortunately because of the time lag, I can not use your program at this time.

Also, other meeting presentation programs that I have tried out, will allow me to block from view anything on my desktop except the particular presentation that I am presenting. Zoho doesn't appear to allow this option. I would prefer that my participants not be able to see my entire desktop and task bar...just the presentation that I want them to see.
Does Zoho have a setting to give me this feature?