why does my computer freeze like this?

[Andy L.]

There are lots of possible causes.
Shortage of DRAM. Windows 7 32 bit can accept to 3.6GB (4GB) and that has a software work around on the web, and 64 bit accepts to 8GB, but in most uses, 1GB allows running with issues, 2GB is the real minimum, almost every new laptop sold in the US is 4 or more GB.

Wireless signal - if in a desktop as the question is put, if using wireless the signal may not be strong enough and there is something called a wireless repeater, or better antennas that can improve that signal. Also I found that in a new laptop with an older wireless modem, an incompatibility causes issues. That happened with my new laptop that I needed a new better wireless modem.

Virus checking - Some software scans inputs slowing it. RAM improves that.

Cache too big - Internet Explorer and other browsers have options of temporary storage and clearing cache. When the storage of cache is large, the searching of that cache is worse than the time saved of using it. CCLEANER is freeware on the web that helps.

Add-ins that could also be spamware - The more add-ins to web browsers slows them. It may not be called a virus.

Slow processor - Some of the old and new CPUs are very slow. Some things get affected by that.
http://www.cpubenchmark.net/cpu_list.php

Internet service speed - either in shared lines that is actually true for most service, bandwidth has limits, speed is purchased, and the service itself could be slow for any number of reasons.
This is a good speed test:
http://www.speedtest.net/

There are so many possibilities, more specifics of what has changed since you were satisfied, or maybe it has always been an issue.
Defrag the HDD, use CCleaner, review your internet cache settings, other things to investigate offered here.