There are a few things you can try, but since you've claimed you're not an "IT guy" I'll start with the easiest solution.
You can roll it back using System Restore, meaning your PC will (should) behave from before you did the update.
This article on the Microsoft site explains it well
The main points are:
Log on to Windows as an administrator.
Click Start, point to All Programs, point to Accessories, point to System Tools, and then click System Restore.
On the Welcome to System Restore page, click to select the Restore my computer to an earlier time option, and then click Next.
On the Select a Restore Point page, click the most recent system restore point in the On this list, click a restore point list, and then click Next.
Note A System Restore message may appear that lists configuration changes that System Restore will make. Click OK.
On the Confirm Restore Point Selection page, click Next. System Restore restores the previous Windows XP configuration, and then restarts the computer.
Log on to the computer as an administrator. Then, click OK on the System Restore Restoration Complete page.
Of course, this will undo all the changes the updates made!
From memory, XP updates would revert some settings to 'default' and as such, the fault may be a simple change but hard to find if you don't know what you're looking for.
You may want to consider why you can't connect, you could roll back the network drivers from within Device Manager.
It could be a DNS issue and things are not resolving. If you know how, you can ping your router and see if there is a response and then try and ping an external source, such as 8.8.8. This will prove where the fault is. you can then review if you're using dynamic or static IP and if the details are correct.
Open Command Prompt and type ipconfig /all - if the whole page says multimedia disconnected (or similar) then the fault is the machine can't see the card and is more tricky.
Edit
Based upon your comments, please consider
Click on Start, click Run, type services.msc, and then press ENTER.
Search for the below mentioned Services. Right click it and select Properties or double-click it to open the service.
DHCP
DNS
Net logon
Network connection
Network location
TCP/IP Net BIOS Helper
Check to make sure that the "Startup Type" is set to "Automatic".
There is also a quickfix application on the Microsoft website