Maximum PC

I'm unable to browse internet on my old p4/xp desktop pc, the internet gets connected but it doesn't load any pages at all, neither the browsers work nor any installer application works, it shows connection error, i use a bluetooth or USB connection via my cell phone,. I can browse internet via the same connection on my laptop but not on my desktop, is it some virus/spyware or is it some hardware/software settings issue? how to diagnose the problem? please help...
and yeah also suggest me any portable anti-virus that I can take from my laptop to my desktop because there is no internet on my desktop so can't update anything...

I recall from my LAN party days as a kid that if you ran a combination of the network wizard (in Control Panel) and restart the computer, it usually clears up network problems.

Also make sure your modem is actually getting internet.

I have often seen xp assign 127.0.0.1 as the IP address. I would check this as well. If you know your mobile hotspot assigns 192x addresses just manually set your computer to use 192.168.1.x then reconnect to the phone. If that isn't it then also look at your DNS settings. If you computer is looking for a DNS that doesn't exist anymore (or is slow) it can cause the same issue.

I want a portable anti-virus or a portable anti-spyware that is updated and can be transferred to my PC via my flashdrive as I would like to remind that the same connection is working fine on my laptop with the same app and settings..so I guess there should be something wrong with the PC itself and not with the connection and stuff...

if you suspect there is something else that should be done prior to this, let me know please...thanks for the help in advance...

The only one I've been able to transfer to a thumb disk and run was Malwarebytes Anti-Malware

But again, tinker with the network settings first.