restrict users to control uplevel directory

[chings]

currently , my website locates at xxx

and the website url is http://www.xxx.com/

i want to let my users to create their own website under the root , e.g yyy

http://www.yyy.com and create the directory xxx/yyy

1. can i disable them to use php?

2. can i impose some restriction to them , such restrict their authority to modify the uplevel directory , such as dir , unlink

i'm using winNT in my server ,t hanks

[TheIceman5]

www.yyy.com is a totally new domain that needs to be registered.
just run plesk control panel, that will do most of stuff u want

[chings]

sorry , the path should be http://www.xxx.com/yyy