EDIT: I dunno I just went to go try it and now it works, but thanks for all the help!Trojan warning on MTA:VC is an anti-virus bug... software is getting paranoid. 
Regarding sudden speed, you need to check your PC, seems like some parts might be giving up or are busy, then suddenly start to work normal.
If you overclocked your PC, time to turn it back to non-overclocked state.
1. Okay
2. Everything works normal on other stuff and games and I have a custom built PC. Here are my specs, I dunno if t's overclocked(Also SP3 has nothing to do with it because I had the problem before SP3 and I still do:
--- Specs ---
Windows XP Professional Service Pack 3 (build 2600)
AMD Athlon 64 X2 Dual Core Processor 6000+
2.01 GHz
2.00 GB of RAM
NVIDIA GeForce 8800 GTX [Display adapter]
WDE L2046NV [Monitor] (20.2"vis, September 2007)
3.00 gigahertz AMD Athlon 64 X2 Dual Core
128 kilobyte primary memory cache
1024 kilobyte secondary memory cache
Board: ASUSTeK Computer INC. M2N-SLI DELUXE 1.XX
Bus Clock: 200 megahertz
BIOS: Phoenix Technologies, LTD ASUS M2N-SLI DELUXE ACPI BIOS Revision 1102 06/20/2007
2048 Megabytes Installed Memory
Slot 'DIMM_B1' has 1024 MB
Slot 'DIMM_B2' is Empty
Slot 'DIMM_A1' has 1024 MB
Slot 'DIMM_A2' is Empty
HardDrives: C:\ (NTFS on drive 0) 750.15 GB 533.56 GB free
HardDrives: F:\ (NTFS on drive 1) 750.15 GB 715.66 GB free
--- Specs ---
I think thats everything I saw that was important, if you need anything more let me know I will try and find it.