There are web-based tools that can be used for the PC as the client like showmypc.com or ammyy.com. However, if the client PC is unable to install any app (i.e. it requires Administrator priviledges), sorry pero hindi ka makakapag-VNC. Ask for permission from your network administrator para makapag-install siya. Or try the built-in "Remote Desktop" app in Windows kung gagana. But still, Administrative Priviledges are required.
Telnet into switches, routers, and PBX? Yes, you might want to try SSH as an alternative.
Pero based sa post mo (wag mo masamain)...are you planning to do this at work or school? Make sure you have permission.
i was actually looking for the built-in "remote desktop", so i won't need to install any client side app. also telnet, so i won't have to reconfigure our switches.
i'm actually a system/network admin in our office and i'm trying to use my phone for it. telnet lang and remote desktop ok na.