What would be the main cause that makes computers behave slowly?

There's allot of thing that can make comp run very slow. If your problem with download speed than you must check the network, It's possible that your comp also download update at the same time you download adobe, this will reduces your speed since it download two thing in the same time. To over come this you can turn off automatic updates. Right click my computer -> properties -> automatic updates

It's very hard to say. Process management is pretty complicating. What enables OS manufacturers to make so much money, isn't entirely how pretty they can make the GUI look, but how well the OS can manage processes, filesystems, and hardware resources. The youtube problem is likely a bandwidth issue. Other processes are using the bandwidth with your web browser. When bandwidth usage is heavy this can cause problems in the performance of bandwidth dependent apps such as youtube videos. One way of solving this is to pause all other downloads you might be running while watching youtube. Another would be maybe close unnecessary things out of your RAM by using the task manager. Also, you can set the priority of the browser you're using to watch youtube to a higher level, or set other processes to a lower priority level. Giving Firefox or Internet Explorer more CPU usage time improves the performance of your webrowser and thus makes Youtube run better. But, this is at the risk of other processes not getting enough time to run properly.

dude there can b many resons

1)low memory...that is u need to have atleast 512 mb or 1 gb of ram for the best performance..the RAM must b ddr or ddr2 ram...not SD RAM.

2)depends on the processor speed ...P4 has 3.66 and like that varies

3)virus problem or spy ware....download spybot software and scan ur pc

4)low space in C :

5)remove ut start up files..taht is goto run and type msconfig and click on stat up and unckeck all ths loads pc fast

6)delete the temp files

7)do defragmentation every week ,which will help to speedf the pc

8)remove unnecessary prgrams

9)update ur windows

10)delete recycle bin

Definetly, virus and or Malware. Run antivirus programs and spyware removal tools.

Spyware can actually download stuff onto your computer, resulting in a slow connection. Make sure to keep it clean!

Turn your virtual memory up, do a disk clean and defrag religiously!

When you do the diskfrag, make sure your antivirus is running, so it can catch any bugs that are released by the defrag process.

If you need to know how to do any of this, step by step, just click my profile and e-mail me.

I will be glad to guide you through it .

It could be the XP programme that's slowing it down. Go to control panel, then click on Software explorer and check that you haven't any programmes slowing you system down. Have a good day.

ur os is not supported with hardware.for better performance u can try windows server(2002) or u can extend ur RAM capacity

you probably have hardly any ram.. wich is the thing that makes ur computer go slow or fast..

u must clean up you disk......