Computer’s Acting Up

All of a sudden my PC has gone nutty. Random lag spikes in games, and when I’m downloading, with nothing else running on the background it uses most of my resources – 90 ish percent of my 4 gigs of ram. Here are screenshots of CPUZ.
Please make suggestions of things that don’t fit!

Thanks alot
It’s been really frustrating
Answer #1
Have you tried running any anti-virus software?
Answer #2
Have you tried running any anti-virus software?
Try this and then do a defrag and maybe get rid of unessecary files?
Answer #3
Trojan perhaps? A fragmented HDD isn’t going to cause random lag spikes or anything else you described. But maybe run Malware-bytes anti-malware, ccleaner, and do a scan with an anti-virus program. Don’t do it all at the same time and after each scan, restart.
Answer #4
do the following steps:
1. go to command prompt then type, “dir /ah” without quotations. check if something appears. if something appears like “RECYCLER” it has been infected with virus.
2. open task manager (ctrl+alt+del) go to PROCESSESS, click MEM USAGE and check which application uses most of the memory.
3. do some some defragmenting, like others said.
4. download an antivirus like ESETNOD32.
hope this could help you.
here’s my email address: @yahoo.com if you have some further questions.
Answer #5
try this way, its easy and fast if this works Install latest version of Malwarebytes’ Anti-Malware , update it and start full scan after that remove everything it shows that it will harm the pc, than restart
Answer #6
–> Helpdesk
Answer #7
THanks for all the help. But I’ve had malwarebyte running for a while, and I just scanned it with no infections, so it’s definately not a virus. Here’s a shot of my task manager.

Answer #8
get a startup manager and kill some of your auto load apps
looks like your memory is not running up to snuff, it’s at 373.2 and should be 400 MHz
it also looks like you have only one stick of memory and are running in single mode
adding another 2gb stick might help
you made any hardware changes lately ?