Audio is slow and choppy

I'm using a friend's laptop(Acer Aspire 5517 with W7). It was really slow at first but I did a registry clean and now it's back to normal speed. But his speakers or whatever's causing this is just horrible. Every sound that comes out of this is slow and choppy. Even the windows alerts. The audio has been great before for a few seconds, then it went back to being all laggy. Any idea what this could be?

almost forgot; it has the same problems even when i use headphones

Hello there.

The laptop could be infected by Virus/Malware and other threats, you should perform a scan in safe mode with Malwarebytes' Anti-Malware

Malwarebytes' Anti-Malware: Malwarebytes

Other thing you could try is to update the Audio drivers.

Last but not least, don't use a registry cleaner if you don't know exactly what are you "fixing", it could lead you to a much bigger problem that the one you had on the first place registry cleaners do more harm than fixes.

The only one you should "trust" and with the quotes i mean do your backups before it's with CCleaner which is awesome.

CCleaner - Optimization and Cleaning - Free Download

Thank you for all of your adive, but now I have another problem.
I let it scan, then it gave me a ton of infected items, so I deleted those infected items. After doing that, it told me to restart. It starts up fine, goes to the login, but when I log in, i get a black screen. It's so strange because I can use ctrl+alt+del to get to that window with the row of options and I can even run task manager, but that's all I can do. I tried system restore and it said nothing was changed. Did i screw up or am I supposed to wait until the desktop comes up?

what do you mean by "Black Screen"? you can't see anything?? not even the taskbar?

Nope. Nothing. Well, other than the cursor, but it's not doing me any good at this point.

could you open by ctrl + alt + supr, task manager, click on file, run and then write explorer, hit enter and see what happens.

Have you performed another scan in safe mode to be sure that there's no malware left?

Also, try to perform a System File Check! one or more files could be damaged by the malware

http://www.sevenforums.com/tutorials/1538-sfc-scannow-command-system-file-checker.html

I ran the first option in Repair mode. Don't know if that worked, because it said it couldn't be repaired, but the dektop finally loaded. man what a relief

once again, thank you for your help!
i guess i'll try updating the drivers this time

Always when you scan for virus/malware, try to do it in Safe Mode with Networking (F8 on BIOS) to ensure that the virus is not running when you scan for it.

Also, after you removed the malware, always do a SFC to ensure no system files were affected, and if it were affected, SFC will take care of it.